FWB? Should I tell him?

I have been wanting to have a kid for a while now. I just seem to pick guys that are jerks, and I wouldn't want my kid around them. I am so over relationships. My best friend and I were talking one day and we decided to become fwb. He don't want a relationship either. We have been messing around for a little while now. I stopped taking my birth control like 2 months. He seem to think he can't have kids because he is almost 30 and hasn't a kid yet. If i become pregnant, i am gonna tell him its not his anyways.. am I in the wrong because I haven't told him I stopped taking my birth control?