Your boyfriend should never be mad you say no to sex, regardless of what the reason is.

Being afraid to communicate can have it's toll on a person. But I can see his side also...being unfulfilled is disappointing, probably for the gf as well. You're gonna have to get over your inability to communicate some how.

You should tell him. If you were to have sex and vomit during that, he'll think it's his fault. Isn't sitting in a shower a bath?

well sit down in him two birds one stone

Just do it badly and he won't ask you again. This works for lot of other things too like cooking or washing dishes.

Well, couldn't you just sit down on his cock..?

Tell him! And shower sex is overrated. If your on a chair maybe you can do something he would like wink wink

What is embarrassing about that? So you have to sit in the shower.

First of all, as some people said earlier, your boyfriend has no reason, I mean absolutely no reason at all to be mad at you because you don't to have sexy time. It's not something he is entitled to and if he is always like that, you may want to rethink that relationship. Cause that's a tiny red flag. Second, is that vomit-while-in-shower thing something you have an explanation for? Because if not, you may want to go to the doctor/hospital. Good luck

TALK TO YOUR BOYFRIEND...Men have feelings too. His feelings are just as valid as yours. After getting rejected for the umpteenth time, he's probably not really angry so much as feeling insecure. Tell him your reasons!! If he is still mad? Thats a different story.