How can I convince my boyfriend that I'm not having sex with my dad?

My boyfriend thinks me and my dad are having sex. How can I convince him that this isn't true? He thinks this because once I sent him an email about my dad saying I'm not the father when I was pregnant with my boyfriend's baby. He also said I take care of you and put a roof over your head, as if he's in competition with my boyfriend. He says all my boyfriend cares about is money. Now my boyfriend says Leave me alone, and he's threatening to change his phone number. What can I do to make things better between us? He's the only one I ever truly cared about. How can I make things between us work? I never had anyone really care about me before, and now that someone great is in my life dad wants to get involved. He only cared about porn magazines before. I really care about this guy and I don't want to lose him.