Lesbian but you have a child?

I am a lesbian and it feels really good to say that. I'm in the process of coming out to everyone close in my life. The only people I have left are my parents.

My brother already knows but I didn't purposefully come out to him. His GF saw a facebook status of mine about coming out and he saw it on her feed weeks ago. He hasn't said anything to me or our parents but he told her he thinks it's cool. He and I aren't close at all, actually he used to be very abusive towards me when we were younger so that made me happy.

I live in a small city and we live in a bible belt so not a lot of open minded people. I hide, denied, and tried to fight being a lesbian. I went through a big depression and started cutting myself because of the pressure. Because of such I had a lot of one night stands with guys. I've never felt anything with a guy other than friendship so I kept trying. I got pregnant five years ago. This year his father came back into his life and we tried having a relationship- he still loved/loves me and I felt like I had to be in a relationship with him so he'd be in my son's life.

I just don't know how to explain how I am a lesbian when I have a child. What do I tell people when they ask? I'm on an online parenting forum and I've had people tell me "you can't be a lesbian you've had sex with a man"