First off he needs to be tested for stds. Also you need to be sure to get tested yourself. I would abstain for atleast 6 months to a year and make him get retested because HIV can take 6 months, a year, or even longer to show up on a test.
There are quite a few things he did wrong here. 1. He went to a stag party at a hotel, 2. He got drunk, 3. He did cocaine, 4. He cheated on you, 5. He kept it from you for a week. On top of all of this you sleeping with him now is a major health risk. If he hardly remembers the incident and didn’t know the woman, he probably didn’t use a condom. That means even greater chance of him contracting something.
If both of you want to work it out enough, you can, it will just take a lot of work. Both of you need to go to counseling and you need to set up rules and boundaries for him to help put your mind at ease at what he is doing. Here are some suggestions, you may want to make sure he doesn’t go out without you, you may want to have access to his email accounts and phone to make sure no inappropriate things are going on there, you may want him to no longer hang out or associate with the parties that encouraged these kind of activities.
Honestly, I’d just say leave the guy and pray for his soul. Also, did he have these problems before? Maybe you could get an annulment if this behavior is not new. It sounds like he’s probably done this stuff before. Also, why would you let him go to a stag night? I’m not shaming you for it, but stand up for yourself. I’d never let my future wife go to a bachelorette party unless I was sure nothing like what your husband did happened. I say forgive him, leave and move on
Please, please, please protect yourself.