Confused🤢

Well first of all, have you guys ever felt that feeling where you feel nauseous/ no appetite/ butterflies/ super quick heartbeat and just sick to your stomach in general? I’ll get this feeling usually when a guy likes me and I like him, or if there’s a chance of dating. I’ve never been in a relationship or done anything and I’m 18. So anyway, this guy has been kinda flirting with me and we’ve become closer, and I’m starting to get this feeling. I don’t think I like him, I like his personality but I just want to be friends. Why do I feel like this? This feeling really really sucks