Unhappily married?

I'm a young, newly married woman who's possibly made a mistake! My husband is one of the most wonderful people I've ever met. We were together for over six years and lived together for two years before marrying. My problem is that although I know I should be very happy, I don't feel that way. I'm not unhappy (sometimes things are fine) but am discontented. It got worse about year ago (when I was engaged to be married) when I met this guy who I got on very well with. Nothing happened but we stayed in touch and have since admitted we have feelings for each other. I know I'm going to see him again soon and that my husband will be with me. I'm worried about how I will feel. I think I would be stupid to let anything ruin my marriage so early on but also worry that maybe fate is trying to intervene, telling me I did the wrong thing in the first place. I did try to talk to my husband before the wedding but couldn't get the right words (whatever they might be!) out and he thought I was just looking for reassurance. I feel it's not just to do with the other man (he's maybe only highlighted problems that were already there). In the back of my head I've always felt there was something missing. However, I honestly believed I was just being fussy (watched to many sappy romantic movies and expected life to work out the same!) as we're actually a great partnership and that I would settle down after the wedding. They haven't. I feel extremely bad for thinking this way and has been putting a strain on our relationship as, to be honest, it can contribute to making my moods unpredictable (for no reason he can see or that I can admit to, I feel bad). It's unfair on him as he tries so hard to make things work. I'm soooo confused!!! Can anyone offer any opinions/advice?!