Hi and welcome to our crazy little group

It's very true getting married and all of the changes it brings can definitely bring on anxiety

It may be hard determining if it is normal jitters or a major doubts. Obviously I don't know you so I can't say for certain what is really going on. I think I'd look at a few things---
1. Are you normally more anxious about things? Do you ruminate over most big decisions? If so then this could just be an exaggerated form of cold feet.
2. Why are you getting married? do you love him? Are you marrying him because of a situation---pregnant, need money, trying to get out of a bad family situation..... If you are marrying him primarily for any reason other than you love him and want to spend your life with him, then you may need to look hard at getting married.
3. Is there a big "elephant in the room"? What? Is there something in your relationship that is problematic? Do you have a secret he doesn't know about---money issues, other relationships...? Do you trust him? Is their any abusive behavior on either side? How do you get on with his family? His with yours? If so, you absolutely need to talk about these things, before getting married.
My husband and I are Catholic (which is neither here nor there) but in our church couples have to go through classes/or counseling prior to the marriage. My husband and I were 'lead couple' for several years in our home. Basically we took engaged couples through the classes and encouraged them to look at the issues I've listed above. We, honestly, had one couple that looked like a train wreck. We tried to get them to look at issues but they just couldn't. The priest, who eventually married them, came back to us 6 months later telling us that they had already split up!! This couple just couldn't reasonably look at their problems. Then we had another couple that we worried about because they never talked about major things in a marriage---what if they couldn't have kids (which was a possiblity for her), money (neither one knew anything about the others money), how they wanted to spend their own private alone time etc. We were very worried about them. I think, though, once they realized they had a lot to talk about, they got to work. As of 2006, they have 2 children. I know they wanted to join our group to be a lead couple. We've since moved so I don't know what's happened to them.
So...... even if you have some issues in the relationship, if you are willing to work on them, then marriage is fine. If you want to sweep them under the rug, like our denial couple I mentioned, then you should not marry.
I hope this is helpful. And I hope you go on to a happy, wonderful marriage.