I'm 18 and I haven't had a period in 6 months. My period has been irregular one time and i came on the same month i was suppose just late. Me and my boyfriend was having unprotected sex at the time. I have had urine test at home and at the doctor, they all come back negative. I have no symptoms but weight gain and sharp pains in my stomach from time to time, also when i get upset. No sickness, sore boobs or any other symptoms. What should I do.? Is there anything that could be wrong that i need to get checked out ASAP.??