Has anyone ever broken up with someone because they just didn't love them anymore, and then regretted it?

I have one of those boyfriends you could call a typical girls idea of 'perfect'. Hes attentive and sweet, never goes a day without showering me with compliments/affection, puts me as a number one priority and always supports me no matter what. He always talks about our future as if we will be together/married/kids etc and puts so much effort into doing spontaneous cute suprises to spoil me!! (yes its hard to believe). On top of this he is gorgeous and athletic and girls always stare at him when we go out. HOWEVER, lately ive been really struggling to feel like I love him- he's younger than me (20- im 21) and im the first girlfriend hes had. I think to some extent hes very dependant on me, and I feel like I really have to 'mother' him. I worry that we got together so young (he was 18), and that he hasnt had time to figure himself out. When we met he gave off a real 'bad boy' vibe, but since we got together hes been nothing like that. Ive seen him act like a different person around his friends and I find it hard to believe someone so inconsistent about who they are can be sure of the person they want to marry. I really feel older than him and I wonder if him 'spoiling me' and always agreeing with me is genuine, or whether its because he 'needs me' (he doesnt have a very strong network of friends, and ive been with him since we left highschool). We have been in a long distance relationship for 2 and a half years, but manage to spend more time together than apart (longest time apart is 3 month, longest time together 5 months non stop!!). He can be very over-sensitive and needy. If you asked me if I felt I was in love with him, id say well no. But hes such a great catch 'boyfriend quality wise' and I wonder if i will regret it, and if im drifting away for the wrong reasons. Advice? Should I stick it out and wait to see if he grows up and becomes more stable in himself? Or should a 21 year old having doubts go with her gut feeling?