Okay, this will sound really strange especially to none WoW players but here we go. It may also seem like something that's not a big deal, but the fact that it's messing with my real life has suddenly made it a real life problem.
I have a level 85 hunter and really enjoy playing. I have mainly only done battlegrounds and old content raids with friends for fun. I have okay gear (some Zandalari heroics, some Firelands epics and a bit of PVP stuff that needs replacing), my dps is pretty good (18-22k on dummies, anything up to 25k single target questing) and I'm not too bad at picking up tactics and handling multiple things at one.
However, my friend has a really good raiding guild who invited me and my boyfriend to go along and do Firelands with them. I had never raided before so was thrown in at the deep end (all the bosses up to Raggy). I also suffer from my nerves really badly so I didn't know how well I was going to cope. Our raid leader is really nice and told me not to worry, but he loses his rag quite easily if we screw up, as do the healers. I understood tactics fine but when it came down to the fight I would get so flustered and panicky that I really screw up (tab onto the wrong target, run into a tornado etc.) When someone tells me off I can't cope with the pressure and it makes me mess up even more. What makes it even worse is that I can barely hit 15k, even when I'm just straight dpsing.
I'm on my third week now and I can't stop thinking about having to go back on Thursday, it feels like I have a dentist appointment to have all my teeth taken out. Every time I think about it my head throbs and my neck swells up so I can't breathe and I feel like I'm going to have an anxiety attack. I tried going out with my friends last night and I found it hard to enjoy because my anxiety levels are so high. What makes it worse is that I've found out that this is my last chance before they kick me out because my dps is too low, so that will be all I can think about all the way through the raid.
I'm really tempted to just tell them that I don't want to go. The problem is that if I do this then there won't be enough people for two raid groups so I will mess everything up. This is my best friends guild and I am really grateful for them giving me the chance but I really can't cope with it. WoW was always something fun that didn't mess with my real life but this is a nightmare for me. I can't stop thinking about it, I wish I had never gone in the first place.
So what am I supposed to do? Do I suck it up and go along? Even though it messes me up. Or do I stop going and mess everything up for them? I know the raid leader has a lot of bad things going on with his real life and he is fed up of everyone making things difficult for him. I'm really stuck :c

Try not to stress yourself out about this. Raids require a lot of teamwork to complete, and may be very offputting to those not used to having to coordinate with so many people at once, but there is fun to be had in this.

You have to let yourself have fun with it though. The more you wrack your nerves about this prior to raiding, the more prone you'll be to accidents. Try to relax, I'm sure you have your own methods of relaxing yourself, try a few of those while raiding.

I don't play WoW anymore, but the basis of raiding hasn't changed since the earliest days of the game. You just need to accept some of the realities of raiding. Perhaps most importantly: everyone will screw up at some point.

Back when I was main tanking raids like Molten Core, did I screw up? Hell yes I did. Although raids were the size of 40 back then, one screw up SOMETIMES didn't mean a complete raid wipe, it did result in a whole bunch of deaths. And with one absent minded screw up, I die and cause half the raid to die along with me. Yep. That was ENTIRELY my fault. Woops!
But I learned from those mistakes, and everyone else did too. And most importantly, I laughed about it. Even if plenty of people got mad at me, I laughed about it. Why so serious!?
Part of the adventure of doing new raids is that you're not sure what you're in for, and you're not sure how to handle what will happen next. A lot of times, especially when you're new to raiding, this usually ends up in you dying or not being able to maintain your damage output.

Take it from me, you're far from being the only person going through this, and people have been going through it ever since the beginning. It can be overwhelming, but you just have to keep trying. In the meantime, just relax about the whole thing and look forward to your next raid experience.

Even if you're being pressured, stay calm. Even if you don't know what's going on, don't lose focus. Ask your guildmates for tips. Whenever newcomers would join our raids, it's a given that they need time to learn.
And most importantly, have fun. Don't take it as an obligation to your friends against your will. Take is an opportunity to learn.

Look you said WoW is fun for you, and you don't seem to like the new raiding seen. That's fine so do a whole bunch of other people (myself included). But don't let your obligations to your friends ruin your fun. You said you don't want to betray your friends and say "no" right? The just tell them that you don't want to go to the raid, if they really are your friends then they will understand. If they tell you that you have to go, then they really aren't good friends. Also if you really like the guild, ask them to help you get better at raids, let them take you through lower raids and let you get a more level head for that type of thing. Raiding is not for everyone so don't feel inclined like you have to. Its a game and that's very important to remember, games are meant to be fun. So don't stress, if you don't like the feel of raids then just don't do it. simple as that.

google search for best raiding dps specs and try the new spec. is the 22k dps against a Heroic dummy or regular 85? there is a big difference, mainly you need to be hit capped. gear and or changing set bonuses in the enchant shop should help. another way to do this is find a hunter on your realm or guild that kicks ass and copy their build, gems, enchants, and learn their rotation of shots. you must practice this.

if the above doesnt get u the dps u need, then apologize and excuse yourself from raiding. if the game is causing so much trouble, relax and find what works for you. they can always recruit another, dont feel captive to them.