Sorry for the delay in getting a response to you.
While it may be only human to sometimes think about that situation, it would be a mistake to put too much emphasis on it. The situation happened after you had a few dates, but it doesn't sound like you had both agreed on a committed relationship.
You also have the reassurance that you know exactly what happened...both parties have acknowledged their behavior. If there was lying involved there would be more reason to be concerned.
I'm sure you would not want your girlfriend to be obsessing over how many women you've been with, since you mentioned in your note you've been with a great number of women. It may also be possible that because it's been easy for you to be with a lot of sexual partners, you think that everyone will be as sexually active as you have.
If this relationship is going to work, you need to focus on the future, not the past. It sounds like limiting alcohol intake would be a good idea too, as drinking clouds judgment.