Just found out I'm pregnant with my ex's baby, should I tell him?

I'm normally all for the father being in the child's life, even if the mom doesn't get along with him. But my ex is a piece of shit and I don't want to tell him, and I want to know if you guys agree with my decision. My ex is an alcoholic, we broke up because I found out he was cheating and also begging people for Adderall and Ritalin. He already has 3 kids from 3 different women. He doesn't have custody of any of them and none of the moms want to let him around the children because they don't trust him. He acts like he wants his kids around, but when I was with him we had his son for a little while and he did absolutely nothing for the poor kid. I got up with him in the morning (4 yr old) put him to bed at night, fed him, bathed him and everything with no help from dad. Is it right for me not to tell him?