He's the One for me, am I the One for him?

Okay so I've been with this amazing guy for the past 3 years and I love him more than I thought possible. With hardships of the past, I never thought I would allow myself to be as close and intimate with another person but..I am♥️Point being, we have been talking lately that we want to get engaged (and married later down the road for financial reasons). Hell, we've been talking about the idea since the first year of our relationship and granted you never really know if they're the one but he has convinced himself that I'm his true love and it's been that way ever since he first laid his eyes on me. I love this man to death with all my heart and he is so perfect to me. He has CP but you could never tell; he's the smartest man I know, he's never been in love or had a serious girlfriend before yet he has the biggest heart and does all the things a man should know to do and be as a good companion. It's like he is this perfect human being who was made just for a very special someone, but he is so amazing that I'm scared I'm not good enough for him. He says that he's a broken man beyond repair and that's he's not good enough for me, that's he's the lucky one to have found me, but I feel the exact opposite. He's too good for me, I wish I could be as amazing and wonderful as him. I don't want to say yes to him ONLY because what if I'm going to be ruining his chance of finding someone better, meant for him more than me? I'm far from perfect, he tells me he never looks at other girls that I'm the only one in his eyes, and he is the only one in my heart  yet sometimes my eyes look; it's natural I can't always help that it happens sometimes, not that it ever goes past that glance at someone else. It doesn't mean I don't care for him I do it's just instinctual. I just.. I want nothing more than to spend my life with this man but is it wrong that sometimes only very few sometimes when I think about wedding rings and engagement it doesn't make my face brighten or my heart skip a beat, every single time. Isn't that supposed to happen when your in love or am I just reading too many books about fairy tale love and I can't measure up to it. I love this man and will be his world and everything if he asks me, I just don't want to ruin it for him. Can someone tell me if I Am I just being unnecessarily over dramatic or what? Please, I need some advice. 
(I'm sorry this is so long but I appreciate those who read and comment)