I love my girlfriend, i enjoy in the moment kissing her, but about 5-15 minutes afterwards i feel sick to my stomach and like i wanna throw up, i know i love her but i don't know why kissing her makes me feel sick?

Does your girlfriend wear make-up-lipstick if you are kissing her lips? If so, perhaps you are reacting to the make-up she is wearing. The next time you are going to be with her, ask her to not wear any lipstick and see if that solves your problem. If it does, then your girlfriend may need to wear a different lipstick since you are sensitive to it. Hope this solves the problem! Good luck!