Should I get a divorce?

I have always had doubts about my relationship with my now-husband. Before getting married, we had broken up once and there were several times where I thought of leaving him. Eventually we got married because he did not want to live in sin any longer and I thought it was the right thing to do. I love him very much, but I am not always very nice to him. For some reason, I tend to become a little more abrasive when I'm with him and I hate that about myself. I am very young, 21, and I feel like I am missing out on a lot of other things. He is a the nicest person I have ever met, but I feel like I do not love him as much as he loves me. He is so sweet and nice and I'm not sure why I do not feel more in love with him. I feel like staying in this marriage with him might be the wrong choice because he deserves better. I met someone else and have feelings for him, though I would never cheat on my husband. I think that if this marriage were healthy, I would not be having feelings for other people. On the other hand, I'm young and I do not want to do anything hasty. I obviously love my husband, even if it is not as much as he loves me. What should I do?