<human>: I have a great relationship with a guy I have been with since middle school, over 5 years. It's a pretty healthy relationship and I've absolutely not a doubt that he loves me, and he's stayed with me through circumstances which most teenagers would run from. 

However, he is a very complicated guy. His stubbornness defines his entire personality; he will not do something just because someone else wants him to, ever. He has never told anyone he loves them, ever, except me (he tells me multiple times per day). He doesn't respond when even his mother/sister etc. tell him they love him (although of course he loves them too). 

What bothers me is that he will not say "I'm IN LOVE with you" to me, even when I say it to him and chastise him when he says "I love you too" back (he doesn't mind the chastising, we do that). He says it's because they mean the same thing, but to me they don't and he knows that. 

If they really meant the same thing to him, wouldn't he just say it back to me because he knew I wanted him to? I have a hard time not thinking that he might be saying it because, somehow, he isn't sure about being in love with me. This is the only substantial evidence I have of that, but I don't know what else to think of it. Am I just over-thinking things, or is this truly fishy? I'm not sure if I should just accept that it's his stubbornness or if I should worry. 

Note: he has said it here and there, when he really knew I was down and he knew saying it would make me feel better. However, in over 5 years that's only been <5 times.

Has anyone ever had experience with this sort of thing?

Condense the text into a few key points
<bot>: My boyfriend doesn't say "I'm in love with you"; am I just being insecure and he, stubborn? Or should I worry?