Everytime I kiss this guy, I feel sick afterwards??

I’ve been seeing this guy recently and it’s been really fun and a lot of the time we make out or whatever for awhile after hanging out the entire day but each time I make out with him, I feel sick after.. not sick in the way like ew I don’t want to kiss him, I feel sick to my stomach way. Sick as in I have a cold, it doesn’t last for more than 3 days but everytime I see him again and make out, I feel sick again. Does anyone know what maybe the issue?