Is it normal that i'm paranoid about losing my girlfriend?

I recently started dating a close friend of mine, we've known each other for a very long time and started dating back in February, I love her very much, she means the world to me, I care about her a lot and I usually don't mind her having friends or hanging out with them, it's just one friend in particular, he always wants her to be alone with him whilst his own girlfriend is away out of town and it makes me feel uncomfortable, especially when my girlfriend said "he wants me to keep him company". It's making me very worried, even when she brags about how nice he is, I feel less important to her and I'm scared he's going to snatch her away from me. It may be my insecurities considering I've been cheated on and abused in my past relationships, I don't know. She just feels like the perfect one and I'm terrified of losing her. Everyone else, I'm OK with her hanging out with, it's just him, I just think it's weird that he always wants my girlfriend alone with him all the time, she would not like it if I did the same thing with another woman. They're both going to get drunk together later this week and I'm stressing out wondering if he's going to make a pass at her whilst she's intoxicated or worse, have sex with her whilst she's unconscious. I've seen it happen many times with other vulnerable women and it's disgusting. Am I alone in feeling this way? Am I a bad person? I've never met such a wonderful woman like her before, I don't want to be with anyone else, she makes me so happy which is why the thought of losing her destroys me inside.