I am in love with a girl for 3 years. Now with 1or2 months we are going to marry?but I am in a grt trouble?

Now I am not feeling the same attraction towards her and a fear of marriage is rising in my mind. I was extremely crazy for her and since now I love her. I know she can't live without me. she is so emotional so I afraid of telling her my mental condition. HONESTLY I dont want to leave her in lurch. but when I think about marriage and past marriage life I feel panic attack in my heart. This situation has completly destroyed the peace of my mind. I want to marry her n give her some love becoz her life is so miserable. Its a very painfull dilemma. How can I get back my old love and affectionate feelings. I am leaving away from her. I should have happy instead of fear. What should I do. There is very little time. PLzPLz help me to overcome from this tragic situation.