In your previous birth you were a boy who had cheated your girl and went ahead with marrying someone else and she had then cursed you that she will haunt you life after life. Now that you must be nearing marriageable age and she appears in your dreams and the fear psychosis in you dormant gets wide awakened which leads to hallucinations of this sort resulting in your being sick for a few days.
Perhaps you will get married to that boy of yesterlife (as a girl) and the dream could be an indication to that happening in future possibly.
This is just an interpretation of your dream and could remain a dream. Wear a black string reinforced by blowing Gayathri manthra 108 times into it.