My husband cheated....Should I forgive him?

So my husband recently told me he slept with an ex GF from highschool 3 months ago (he's 29 now) he said it was a mistake & that he was drunk & it was around the time we were fighting a ton....he says he doesn't talk to her or hasn't talked to her since then & that no feelings are there. Basically i told him if he has feelings for her to please tell me so i don't waste my time on him anymore. He swears up & down no feelings are there & that he wants to make it work with me. Honestly....when he told me I didn't react like i thought i would. I'm a HUGE crybaby for everything & didn't shed not one single tear. Am i upset? Of course! But....i did sleep with someone else as well about 8 years ago when we were still dating & told him the truth a month or 2 ago. Anyways, I've never had to deal with anything like this before so my question is would you forgive your man? If so, any tips on how to? I told him I'm ok with letting it go if he never does it again of course. I told him if he does it again I'm done. He said it was a huge mistake & he shouldn't have gone that far just because his feelings were out of control when we were fighting. I just don't know what to do or how to handle this.