I agree with everyone above—this is a mistake, to get married now. You rebounded (which is a no-no), then you proposed fresh into the relationship (major no no!), and now you're thinking about your ex (no-no-no!) and your wedding date is approaching? NO.

You're supposed to be excited, maybe edgy and nervous, but THRILLED to be getting married. And you're not. Getting married is not the answer, and staying together may not be either. You should at the very least call off the wedding (maybe that means on hold to you) and get into couples counseling before things get worse. I would also strongly advise that you look into individual counseling — even more so than counseling for you and your fiance. You seem to repeatedly be looking for a soft place to fall. When things aren't working out with your fiance, you start thinking about your ex. When things with your fiance are going well, your ex is probably non-existent to you. Really think about what that might do for your marriage if you followed through with it.

The reason most people wait to get married until they're into their late 20's and 30's is because you need time to grow up, to find yourself, to find what you want out of life, what your place is in the world, and someone who wants those same things. Someone who shares your same beliefs and dreams for life, and have a deep love for one another. It's pretty rare if not impossible to have that at 21. And it's not your fault. Life and getting experience in it, learning! just all take time.

What's the rush anyway? Regardless of the above, you shouldn't get married because you have a lot in common. A lot of people have things in common (like friends!), but they don't run off and get married! Clearly she is not "the one" now, but maybe she could be. That doesn't mean you have to get married to figure that out—marriage is for people that are past that point. However, some people grow up alone without being in a relationship, some try and do it together as a couple (and succeed and fail), and some will figure it out in later life, get together and end up growing apart. It's hard to control the outcome.

I will say this: if you're even wondering if you should stay together, you certainly shouldn't be getting married. Call of the wedding, give it a little time and counseling, and see if you are still feeling the way, if you guys have enough to survive and try to build on. If not, it's time to go.

I hate to mention that there are plenty of fish in the sea, but it is the truth. Would you be much happier if there was a fish out there for you, who was carrying a golf club or loved living in golf country or hanging out on the greens? Something to think about! Good luck.