Relationship advice needed!!

Almost 17 weeks with my second but I’m extremely frustrated. I constantly get the sensation that my SO is always lying to me. I catch him in the pettiest of lies and I’m at my wits end with feeling like I can’t trust someone that I’m trying to make a life and family with. My sons piggy bank money (+$300) disappeared, finding out other people he used to sleep around with and he denies it all. I thought it was a coworker of his that took the money and he claimed that he suddenly quit working there so we couldn’t possibly know what happened. But I just found out he’s been working with him and they are such good buddies, constantly texting about work stuff. Makes me feel like maybe he knows it wasn’t the coworker after all. He will tell me he’s out working when I’ve just spotted him somewhere else, etc. His work is always “needing him to go in” even sundays, etc. I t just kills me because we’ve always had a history of lies years prior to us being this serious. I need help, advice. Please.. 😭