I am so scared my fiance will call the wedding off since he told me he's now not 100% sure he should marry me... I am devastated and my world is falling apart, what can I do?
Oh I do feel for you and I know how absolutely distraught you must be feeling right now. I think the best thing you can do is to keep talking with him and to find help together. It is a good and positive thing that he has been honest enough to share this with you and it might have been hard for him to say it as he doesn't want to hurt you. Better that he is always totally honest with you though so you know where you stand, even if it's not exactly where you want to be standing right now. Please try to keep things in perspective so you can find a way through this.
He is not the first groom to have had doubts, nor will he be the last. And thinking marriage through rather than rushing headlong into it is a good idea, it is a lifelong commitment that should be thought about and that you should prepare for together. Marriage preparation classes are a very good way of doing this and most churches and register offices run them. Relate is also a wonderful resource for couples who need help of any kind and starting that communication with a professional will enable you both to see where your relationship is going and how it can be saved or made stronger or otherwise. It may help to postpone the wedding while you go to Relate, you won't be cancelling it, you will just be giving yourselves more time to to make the right decision.
Please try not to feel you must get married because you will lose your venue deposit or because your parents will be angry or embarassed or upset - these things are irrelevant, however annoying and upsetting. The most important thing you can do is to spend time talking with your fiancee about how you both feel, and how you can both feel better. I know this is a very tough time for you and your friends and family expect you to just be overjoyed with your wedding planning so confide in your closest family and friends if you feel they can help to support you. It will be ok, it is quite amazing what reserves of strength we find within ourselves at times of crisis. It could simply be that he is feeling pressure to rush into marriage or is perhaps stressed out from his job and it is clouding his vision, he may even be depressed. Whatever the issue, you and he need to talk it out and ideally with a professional who is trained to help. I wish you both all my best.