is it normal to have the ick over this

I'm 22f , bf is 26m , we've been together for 4 years and anyway my boyfriend always preaches loyalty is super fucking sensitive over everything, I found it he liked a girls Instagram picture but like one after the other in a row , I think that's cheating and if I did the same I'm sure he'd feel the same way , it's disgusting because he has always preached about loyalty and I think it was him trying to get this girl's attention, he said he didn't cheat or do anything wrong and we've been together for a while but I'm getting the ick so badly , I can't unsee him as this weak person for doing something he said he'd never do , we've been together for 4 years so I just want to know if I'm over exaggerating , the context would really, really help.