Just not...into him?

Now I know everyone goes through this; it's bound to happen, right?
I have been in a couple of shitty relationships, so you'd think that I would be head over heels in love with someone who treats me like a queen. He's a great guy. He's a little childish and immature, but he's sincere, genuine, and insanely smart! I'm getting ready for my first year of college, while he's getting ready for nursing school! He's 20, and I'm 18. Not to mention he's in the reserves for the marine core. 
So bronze, brain, and a good personality...(not to mention he's not lacking in the downstairs department)...
How am I not into this man?
What is wrong with me that I cannot bring myself to want to just rip my clothes off and swoon over him? He's literally treating me the way most women only dream of! 
An example: my senior prom was this year, and I agreed to take my friend. He literally came over after prom, dressed in a suit, and danced with me in my driveway with music blaring from his truck (sure my neighbors didn't appreciate it). That's literally like the most romantic thing anyone has done for me.
Another example: he knows I love chocolate milk. Every time he comes to see me (if we aren't meeting up or going on a date) he brings me chocolate milk or a candy bar from the store! I don't even have to ask!
So...what's wrong with me?