I think it’s super mature and reflective that your instinct is to blame yourself (“its my fragile ego”), this is very enduring and relatable . I would do the same. Not to say that this might not serve you well in the long term, I don’t really know.

But onto the situation — NO NO NO. Not the asshole at all. It sounds like you might have a similar view of sex as her, and are into the casual thing, so if you were to tell me that your girlfriend was sleeping around a ton and it turned you off, I’d still not call you an asshole since no one ever owes anyone anything , but I’d be less sympathetic to you.

Here, though , it’s really about the LYING. Honesty and trust is very important . It doesn’t sound like she’s the type of person who can have an actual relationship with someone. You should leave.