Banging my step brother

I noticed my step brother had a huge cock because you can see it even when he's wearing jeans. We are both 20. So a few weeks ago I was teasing him and tole him to fuck me. He made me cum several times. He asked me if he could cum in my mouth, since he made me cum like never before I let him and I swallowed it. I have a boyfriend but he can't get me off like my step brother does. I like fucking my step brother and now he want's me all the time. He fucked me so hard for so long the other day my pussy hurt for a few days, but I liked it and I let him fuck me anytime he want's. He is really good at eating pussy too. He get's me off so good I don't mind swallowing his cum, in fact I like doing that for him. My boyfriend knows something is wrong because I don't want to fuck him anymore, he stinks in bed.I think I'm going to dump him.