Partner of 3 years won't add me on Facebook?

[millie]

So we've been together nearly three years and we have a 6 month old baby.

It probably seems childish, especially at our age (mid-30s), but I'm concerned that he doesn't want to add me as a friend on facebook. We have a few mutual friends (mostly his, he's only added a couple of mine) and I'm friends with some of his family members but not with him. I admit I sometimes facebook stalk him and I see that he often likes photos of his pretty female friends (he has A LOT of those) and it's making me insecure. I also know from looking at his private messages (not good I know) that a high school acquaintance of his recently got in touch (also very pretty, and single by the looks of it), and they've agreed to meet up in person at some point. He didn't deny it when I talked to him about it, and says it's all perfectly innocent and that it'll probably never happen anyway.

The thing is, I can't even blame the woman for getting in touch because nowhere on his profile does he say that he is in a relationship (also, he's hot). There are no photos of us together (none that I can see anyway) and he never mentions me on his wall - I know because he set it so his 'friends of friends' (that's me!) can see his stuff. The odd friend sometimes mentions me or the baby, but my boyfriend barely acknowledges them and it bothers me. I don't know why it's affecting me so much, but it does. Am I being paranoid?