Boyfriend telling me about past sex life?

I've been with my boyfriend about four months now and he's two years older than me. He's had four girlfriends before me - each lasting about two months or so. I've had boyfriends in the past but nothing serious, and the boyfriend I am with now is the one I lost my virginity to. My boyfriend treats me really well and we get on amazingly. He's told me that he's never loved someone like he loves me, that I'm the best girlfriend he has ever had. He's told me he didn't get on with his exgirlfriends like he gets on with me, and he did wait a long time for me to finally go on a date with him. I truly believe everything he says seen as his friends and family have said they've never seen him so happy and in love like this. The only thing that's bothering me is that fact that he has told me about his past sex life two/three times in the past. I'm not annoyed or anything, just really confused as to why he has told me certain things. He is two years older than me so he is obviously going to have a past sex life, and in all honesty it's no where near as bad as I'd imagine. The first thing he said was that he was having sex with a girl and that his mum heard her moaning. I didn't really know that to think when he told me, but I'm not too bothered about it anymore. He's told me a few times about the positions he hasn't done before which I really wasn't bothered about, and it kind of felt good that I was the first he was doing them with. The last thing he said is the thing that completely shocked me. He told me that he'd had sex with a girl on her period before and that it was really tight and there was blood on the bed after. I was completely shocked and have actually felt physically sick since he told me. I mean each to their own and all, but that isn't really something I'd go telling around - especially to your girlfriend. I don't know whether I'm just being sensitive or overeacting or whatever. This isn't something I'm going to start an argument or cry myself to sleep over, and in all fairness he didn't go into that much detail. I'm really not jealous or insecure about it, just completely confused as to why he has told me - especially the last one. Any ideas? :S

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