Should we break up...?

I've been dating this guy for a little over 2 months. When we first started going out I wasn't sure if I liked him as more than a friend. He can turn me on, but there's not crazy lust or any awesome spark like we're meant to be together. I really love him, but I'm not IN love with him. There's another guy I've dated before who I'm still in love with who still flirts with me who I know I want to be with in the end, and he's dating someone also. Sometimes when I'm not with my bf I find myself wishing I was single so I could flirt with other guys. He treats me wonderfully and he's an amazing guy though, and we have no problems at all in our relationship. I get along really well with his friends. People always tell me how cute we are together. He's not ugly but he's not very cute though, and people always say I'm a lot better looking than him (although that's kinda irrelevant). He says the sweetest things and just makes me feel like a great person. I never want to hurt him but I know I'm being unfair to him. When he tells me I'm beautiful all I can honestly say is "you're really sweet" but I wish I could return the compliment. I just don't know what to do.