Am I overthinking it?

He was honest when he said he would and then he was honestly he said he wouldn't because he knew it was upset you, you have to initially give him the benefit of doubt. 

Problem is if you show that it is bothering you there's more chance that he will because it pushes him away. 

Arrange to go out with your girlfriends that night, make sure you have a really great night and look sexy as hell and make sure he sees you looking like that before he goes out. Make plans to catch up with them afterwards... 

Unfortunately this is a sign that he's not a strong guy. A strong person has good character (honesty, integrity, trustworthiness), displays a positive attitude (cheerful, caring, friendly, forgiving, helpful, and respectful), fulfills their responsibilities (for handling people who are pains in a positive way, for always trying to make a good choice, for taking care of themselves, for serving others), gives their best effort, and demonstrates self-control (of their body, anger, mouth and money).

Hope this helps!

Doesn't sound like he ever offered to skip this party so your options are to either make yourself crazy worrying about it or to try to put it out of your mind knowing you can't really control the situation. The latter would be more productive than the former. 

I think that the moment you step into deciding to try to control what your bf may or may not do when off with the guys for a bachelor party... you are over thinking things. If you have a boyfriend that you can not trust or believe in unless you are at his side monitoring his activities... you've got the wrong guy. So just let all anxiety about this boy's party just slide right off of you. You are not, will not, and should not be in control of what the boys do. You've told him how you feel about it. Leave it at that. It's the stories of what happened after the party that will matter. Leave your pre-party anxiety behind. Strippers and prostitutes can be two very separate things. 

He is who he is.

That's what dating is: the process of two people getting to know each other better.

That's why dating is almost always temporary, almost never long term. As we get to know the person better and better, the person generally proves to be less wonderful than what we are hoping for. And the relationship has run its course. No need for hard feelings, but no need to feel badly about things coming to their natural ending either. 

So now you know him better than you did a few days ago. You know this guy may have been perfectly adequate as a "Mr. Right Now" but he probably isn't a "Mr. Right." You can keep seeing him, enjoying the moment without much caring that it won't lead to anything serious or long term. You can enjoy it while it lasts, knowing that things are moving toward a natural ending. Or you can wash your hands of it. 

Since you are unable to trust him, break up. Without trust, you have crap for a relationship that will not last long.

Agreed with the comment below. He did these inappropriate things with the ex why wouldn't who do them again especially now he's openly admitted it.

Be done with him.

This guy is a cheater and a creep. Stop wasting your time on him and end it. Admitting to wanting to touch a stripper's boobs and then trying to backtrack when called out on it is garbage. You deserve better.