Unusual Period Flow

Hey i'm 19 and i've been havin sex from age 15. More than anything in the world i jus wanted a baby. Many times i've tried by not usin a condom with not jus one of my boyfriends but most of them that i had a long term relationship with and i never got pregnant. Also the past couple days i have been havin unprotected sex with my boyfriend cuz we both want a child but nothings happening. For awhile now my period has been regular but jus the end of october my period came on as usual but a week after it overed it came back on and lasted 2 weeks. For the first week it was very light but by the second week it was extra heavy to the point where i was changing tampons and pads within an half hour. I was scared to go to the doctor because im not really a hospital person cuz im very impatient. Basically i would like to know what do you think the reason is that i cant get pregnant and my period was on for 2 weeks. %-)