Trust

I've been with my boyfriend for over a year and for some reason idk why but I just can't seem to 100% fully trust him. No actual reason, I just am nervous to and i don't get it. I've never caught him doing anything and if I ever do question him about anything there's always an answer but idk I can't help but wonder if I'm being lied to bc of my gut feelings. Or if I'm just paranoid about getting hurt so I push these feelings aside but I just don't get it has anyone felt this before for no apparent reason you just do?