Bad Feeling??

So it's my guys birthday. Yesterday he told me that he was gonna have a short night at work (home by like 10pm) because they were just doing training. But now he's saying that they are asking him to do a bunch of random work and he won't be home until later this morning like 3-4am. We have some issues from where he cheated on me a few months back when we were long distance. So he's not allowed to go out to bars and drink because that's his usual place that he finds hook ups. I have a bad feeling that he lied to me and said they were making him do extra work because he wanted to go out for his birthday instead. Which I honestly wouldn't have minded if he had asked me because I know it's his birthday and the people he works with know me and about us and I actually like and trust them. They don't seem like the kinda people who would condone him cheating on me in anyway. Maybe I'm just over thinking this??