dont know who the father of my baby is

I dont know who the father of my baby is. I dont even know how far a long i am yet but my last period was on feb 22-28 And on feb 2 i had sex with my best friend cause my boyfriend And i got in a huge fight. And broke up for about 2 weeks. I only had sex with my friend once And i was coming off of my period when i had sex with him. The day or maybe later that day my period started back up again. Anyway i went back to my ex bf but we Didnt have sex till the end of the month or until early march. Please help. I want it to be my bf We have been together for 7 years. Since we were Sixth graders i am only 19.