Oh yeah, I take breakups pretty hard, and still harbor a feeling about the few serious past loves that "if things had been different, we'd still be together." I don't know how common that is, or if it is a chick thing, I just know that's how I am.
I used to spend a lot of time on the relationship boards and have written on them (I'm a writer by trade) and I have my own theories based on some common observations.
First of all, men and women typically deal with breakups differently, even though both may hurt as badly. Men like to get their mind off that person by getting involved with someone else. Women tend to mourn first and move on later. Thus his quick marriage may have been a rebound to avoid thinking about you.
As to why they will marry someone else, well heck I've had that happen so many times I used to joke how they "always marry the very next girl" (actually true for me except for 2). I also joke I must scare them out of dating! Anyway, I think a better possibility is that some women make it clear very early on that marriage is an expectation and are not afraid to push the "commit or I'm gone" button. The rest of us whine about wanting to take it to the next level, they usually push us a way, then we take them back without requiring them to make the desired commitment. Do it often enough and they never take you seriously. What's more I think that they begin to become less likely to ever commit.
I have advised friends (have one who wants to marry her guy of 2 years very badly who hasn't heeded the advice) that they have to decide exactly what they really want from this guy. If you are seeking a husband, is he truly the man you can live with for the rest of your life or are you more in love with the idea of marriage? If the answer is positive, then you need to set a deadline for yourself. I don't believe in rushing into marriage, but there are different levels of commitment, including sex, exclusivity, living together, etc. You do have to take into account his values and time table, but if you really want more, you may have to make that clear. Most of all, you have to be ready to say "this is what I want and if you don't share that desire then perhaps we need to part ways," and you need to mean it.
Truth is, if you can't get what you want from someone, then you really need to move on and find someone who can deliver. Most of us are so afraid to lose this partner, that we haven't the courage to stand up for ourselves. For someone who is afraid to commit (or even just happy with the status quo), it may take a genuine risk of losing you for them to make a decision.
You said you did marry someone else. What did you do differently in that relationship that got you to the alter? You may find some answers there.
The other possibility is that the other guy is a true commitment phobic person and even a CP will marry if the other partner threatens to leave. Unfortunately it doesn't always mean they are happy or will be a good and faithful spouse.
I don't know you, I don't know him, but I suspect some of this came into play. I think it also helps to remember that as time passes, we remember more of the good, than the bad. That's how second children are born because if the memories of morning sickness, labor pains, and newborn colic were stronger than the good memories, no one would ever get pregnant twice! It is possible that what you are feeling now has more to do with the good memories overpowering the problems. It is also possible that there were aspects of the old relationship that were more exciting than the current one. No relationship is perfect, so you may be comparing some things.
Enjoy your current spouse. The bird in the hand is definitely worth more than 2 in the bush, and relax, I strongly doubt, even from what little you said, that he was only in it for the sex. Odds are he enjoyed far more of you than that or you wouldn't have been together so long.
