Therapy if you can. Now. Couple's therapy is good but individual therapy might benefit you too because it sounds like you're willing to consider leaving.

He has to put a lot of work in here. He owes you answers. He does not deserve your immediate forgiveness for a lack of emotion from you. This is extremely painful and he's put you through the wringer--you need to take the time to heal and he needs to go out of his way to help you. You're putting in your share of the work here. He needs to give back and work on himself since healthy people in happy relationships don't go cheating.

I am not implying you are to blame for his cheating. You're not, period. Something compelled him to do that, it wasn't you (because a healthy, decent person breaks up when they want to act like this with someone else), and he needs to address it if this relationship is going to work.

I was in a similar situation to you. It had gone on a few months over text; however, it did turn physical. I didn't know that until my partner came completely clean but that actually took awhile and was really the first step in rebuilding our relationship. Honestly, with your boyfriend having deleted the conversation, you have zero evidence that this never got physical. The conversation I saw (that also mysteriously ended up deleted) didn't look like it had gone that far but it turns out that it had.

Incidentally, STD testing immediately.

Lastly, don't rush yourself with this. It happened VERY recently. I've been through it and it's fucking devastating but we've also come out of it with what I consider a happy, healthy relationship. It has taken a lot of work and a lot of high emotions on both our parts, and I imagine most people wouldn't want to put in that kind of effort (which I totally understand--I am not, by any means, recommending most people stick around after shit like this). It has worked for us.

I've been through so many waves of shit with this. Issues cropped up many months later that had nothing to do with anything my partner had done recently. I'm still living with the fallout and I don't know how long that will last. When it first happened, somebody told me that it had happened to her, and that it took her about 10 months to start feeling close to normal again but much longer to stop thinking about it daily. That's been about my time frame--I'm doing a lot better after about a year but it's still not easy and it still hurts.

That might sound melodramatic or not worth the effort. It's okay if it's not worth it to you. Just don't push yourself to immediately get past this; it's simply not going to happen that fast should you choose to remain in the relationship. Maybe you'll get over it next week, but do not be surprised at the duration or further perpetuate your negative feelings by beating yourself down for not being over it.

Feel free to PM me if you need to chat. /r/survivinginfidelity seems to be a good resource. I've skimmed it a few times but it's a bit depressing for me. Others may find the support helpful.