Sit in a quiet area, take a deep breath and question yourself on why are you getting so edgy. Is it generally that you are not ready for marriage or you don’t want to marry this particular person. Take a paper and jot down points of all the things that are suddenly freaking you out. If you are just scared of sharing a physical and mental life with a new person, which is very natural. If you are concerned on sharing your plans and answering to this person for your whole life, than the problem might be a little serious.
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Share your fears
The heart feels a lot better when you share your problems with someone else. Talk to your close friends or family and take their opinions on whether they think you are making a wrong decision. Ask people who are honest and have your best interests at their hearts. Confess your fears in front of your fiancée. As you both have to spend a life together, there needs to be some understanding. The reaction of your fiancée will tell you a lot about his/her personality and mindset. If you still aren't at peace, consult an older person like a priest or a counselor. You could also talk to a marital therapist; they deal with such issues on a daily basis and can offer you a great advice.
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You start getting irritated by the other person’s habits: messy room, lazy, perfectionist etc. it is probably that you are a lot moody nowadays. The mind gets silly thoughts about your fiancee's ex, his friends circle, his pet and such minor issues. These are small issues are no reason to end your upcoming marriage.