Guy's Behavior

My ex is deeply in love with a new one but still wants to have sex with me. How is that possible?

He told me through messages that he wants to break up because he found someone else that has token away his mind. I was shocked because 3 days ago he was being jealous about me going to the beach with my friends and he didn't look like he is losing interest at all. Is it possible to start falling in love with a new partner while being on a relationship and still feel jealous for your girlfriend? When we met to finish things officially I was upset and he was trying to calm me and go for a walk even if the only thing that I wanted was to leave. I told him that I am busy and I have to go and he started asking where will I go and with who. We went for a quick walk and he told me that he appreciates me and he do not want to lose me from his life. I asked him if he loves her and the answer was that if what he feels is what he things he wants to marry her. I was like wtf you know her only one week. I became more upset and he told me that he hasn't slept with her yet because he is serious for her (by the way we had sex after our first date so that made me even more upset). Then my phone rang and I talked for a while on the phone. All that time we was caressing my leg and after I hung up he asked me if I want to have a swim with him at the beach. I said no and he told me that he wants to have a goodbye sex with me. I told him that I can't and that I feel like rubbish and I adviced him if the whole love at first sight thing will be proven bullshit to not come back to me and I left. On the one hand I do not believe that you can fell in love in only one week with someone and if still that happens it is not possible to want sexually any other person than that one. So, I think that it is possible that the whole story is fake. On the other hand maybe men have a different mindset than women. But he told me that he would marry her even if he has seen her 2 or 3 times. So we are talking about being crazy in love. How is that possible?

My ex is deeply in love with a new one but still wants to have sex with me. How is that possible?
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