Irrational fear that my partner is always cheating

Guys, I don't know what's wrong with me, but I've been dating this guy for about 7 months and the more I fall for him, the more paranoid I become.When he's not with me, I always wonder what he's doing. I think of bad scenarios, like he's meeting his gay friends and hooking up with them, or going on Grindr looking for sex and stuff like that.He travels for work and it makes me even more anxious. When he's gone, I really have no idea what he's doing and think he's spending his free time trying to meet other men.I feel constantly sad, almost every day and I can't take this pain anymore. It's like a pressure in my chest.