Do I Have a Right to be Upset?

I (F22) feel so pathetic writing this right now but I feel sick to my stomach. So backstory - I've been on and off in a relationship with a guy (M23) for a little over 3 years. He was my first love and I was his as well as each other's first time. We are also each other's best friend. We decided to end things about a month ago due to a horrible fight we had and decided to remain just friends (for like the millionth time).

However, each time we decide to remain friends, we always end up just fucking and doing relationship things without the label then eventually get back together. Anyways, recently we both decided to join dating apps and pursue other relationships. I've been on a few dates, but yesterday he told me that he just straight up fucked someone - TWICE in the same day.

He kept going on about how beautiful she was but he didn't tell me much else. We tell each other everything. I'm sick. I didn't think I'd be bothered by it but I'm so hurt right now and I don't know what to do. I feel like I have no right to be though. How do I move on from this? I never thought him to be a one night stand type of person. I also don't think I can be sexually involved with him anymore. I can't stop thinking about this and crying. Any advice please? I'm in college and he's in grad school if that helps anything.

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