SEX! SEX! SEX! SEX! SEX! SEX! SEX! Sex!?

I'm 18. Every time after sex I throw up. We use a condom. I don't do head. And there is not way I can get Pregnant some medical thing that happened when I was younger. I've been to doctors no one knows. I've checked net. This is the last thing I can think of. Does anyone know why this keeps happening? Please help!
Thanks to all
P.S.
I don't think it can be motion sickness. I ride bulls, roller coasters, houses, jets, and race
And I don't think its semen, or latexSEX! SEX! SEX! SEX! SEX! SEX! SEX! Sex!?
Are you on the bottom? I had a boyfriend who, the way he did it, would put pressure on my stomach with his. If I had just had food, I always felt ready to throw up. This is why I never did missionary with him. Try a different position. Try having sex on a semi-empty stomach.

PS - You ride houses? How does that work out? Oh never mind, I figured it out, you mean horses, right?
Maybe it's who you're sleeping with.
even though you don't think so, you might be alergic to latex, but I'm not sure exactly, I have gotten nauseus after sex, because it felt like he was touching my stomach, but that might be a reason why too, does it feel good to you at least?
Try a different position, does it happen with you on top?
Is there something that could make you uneasy to do it with him? Maybe see a therapist, you can get sick because of how you feel emotionally not just physically. Is he the right guy for you? Could you be scared he showed/not showed you a ring?