I had sex with a friend of mine on Sept.6 while on my period it was protected. Then my son father and I have been having sex since Sept.7 until now I am pregnant is it possible that I am pregnant by the first guy even though it was protected and I was on my period and it was unprotected with my son father?

Unfortunately you can not be 100% sure unless you have a paternity test done after the baby is born. However, chances are that the father of this baby is your son's father. I say this because he is the one you have been having unprotected sex with and you have had sex with him on more than one occasion.