So 3 years ago my Longterm boyfriend went on a business/pleasure trip with his two guy friends and this girl he was doing a shoot for out of town. They all shared a room with two beds. Long story short I found out that he had slept in the same bed with her for a night or two. I was mad at him but coped with it because I know that nothing happened with them sharing a room and all. One of the guys that was on the trip with him is a good friend. I began to really dislike the woman for it even though he should have given up the bed and let her sleep in it. I feel like they both are wrong. 3 years later he still does business with her and even invited her out with us and some friends. I called him out on it and he just gets upset with me saying that it was a long time ago like I should be over it
LemonVibe 
[Do you trust your boyfriend? I’d say that’s what this comes down to.
If you trust him, then it’s not a big deal.
If you don’t trust him, then I think you have to ask yourself 1) why you don’t trust him, and 2) why you’re still with him if you don’t trust him.
[If you know nothing happened, what is there to be bothered about? IMO your bf is right — you should have either decided he was worth keeping and let it go, or dumped him if it bothered you that much.