Menstrual cycle was for two days only.

I had unprotected intercourse in the last week of april. the very next day i felt dizzy for 5 - 6 times. ever since i am either constipated or feel sweaty even sitting in an air conditioned room. my menstrual cycle was to start on the 4th of may, but it started on 5th late night. my usual cycle is for 3.5 - 4 days. but this time it was for only two days. the intercourse happened 8 clear days before my scheduled date of menstruation. but even till date i feel either constipated or sometimes loose motions. i am also on a weight loss diet but through a proper dietitian since three months.. but over the last two three weeks i lost close to 3 kgs.. is it only in my mind that there is a problem inside me growing or could there be a real reason? i haven't taken the test. also i am tensed because i have my exams in less than a month now. experiencing extremely high hair fall also suddenly. i feel that i experienced a little less flow during my monthly cycle too but i am not too sure.