My unofficial girlfriend “cheated” on me recently, I feel very confused, betrayed, and shocked (23m/20f) (6.5 months)

Trust me I know the logical answer ( you guys were not officially a thing and etc). Do you have to be official in order to be hurt though? There have been so many indications, directly through verbal communication and indirectly through physical actions, that this relationship seemed like it was getting more serious. We’ve had a few talks about us, and one thing I remember is that when I asked her if she did want to try “officially” dating is that she said no but that she wasn’t opposed to it, just wanted more time. Which I respected and made me relax a bit too honestly. Until many other actions made it seem she was trying to get closer to me as well, so I reciprocated in similar ways. Our most recent conversation about us led to her telling me that she had seen/met with a guy (or 1-3 guys) since early January. Which was ok, it was before this talk, but then she hinted it was more recent than I was thinking. And I asked her if it was 1-3 weeks recent (since there were 3 weeks when we didn’t see each other due to being busy and getting sick). I right away from her reaction I knew that was true. And I felt betrayed, like my feelings did not matter or were not considered when she did it. We talked almost everyday during that time too, everyday if you include texting. We’ve both (somewhat briefly) have met each others parents. And we’ve done things that people in their early stages of a (official or serious etc) relationship do before any labels. Like things friends or friends with benefits would not do if they truly wanted to stay that way. Obviously theres the health issue, Im angry about that. We were going to have sex before this conversation and would have if she did not say that she did see these other people. But ignoring that idk what I could or should do. I am asking for advice, don’t tell me what to do, just either what you would do or what I can do. Technically no one is “wrong,” but cheating and relationships aren’t black and white, yes or no, theres much more involved. Especially when there are multiple examples of her showing that she does care and would possibly want to be closer in the future. Examples that people not interested and people that would want to stay as friends and only friends (or fwbs) would not do. * I have had both fwbs and serious relationships in the past, I guess this is the first time where I met someone who fits the “can’t have your cake and eat it too” saying. She is less experienced when it comes to serious relationships, which was ok, but this is too recent and to interconnected to me (we might’ve hanged the same weekend/day she was with one of the 2-3 other guys) to not feel terrible. I say I’m confused because the past two days I’ve been going through a rollercoaster of emotions when I think about it, which right now is a lot.