<human>: So I've been dating my boyfriend now for about 3.5 years. The relationship is really good. We get on really well, share a lot of interests and make each other laugh. We argue maybe once a year and bicker monthly or so. But we never shout or insult each other and theres always a lot of respect and trust in each other. I told him I loved him about 1 year into the relationship and he said he wasn't ready to say it back. Thats fine, would never want to rush him into saying something he didn't mean and I appreciate his honesty. I tell him I love him roughly once every 6 months. Not enough for him to feel I'm pestering him with it but just to make sure he still knows. We both tell each other we like each other a lot and have had a number of serious and casual talks about our future, moving in together and him making career decisions based to some degree on our relationship. So it sounds all good and maybe its silly for me to even be bothered about it, considering I do feel loved and like he appreciates me. However I read someone else's post on here which was roughly about worrying that they could get on forever but that what if he never really fell in love with her.

Bit of background: his relationship with his parents is fine but distant which makes me think maybe he's scared of being vulnerable. He's also been in two other long term (>4 years) relationships. He's told me that the next woman he says he loves, he wants it to be forever with. And I'm about to finish my masters and start work which he worries will change me and our relationship and then maybe l'll not want to date him anymore. So I know that to some extent hes insecure about that.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: is boyfriend of 3 years not saying he loves me worrying? Is he a serial monogamist?! Or is it just vulnerability?