Am I wrong for not telling my Husband. Everyone says just keep quiet because its probably my husbands. Help?

In november me and my husband separated after being married 7 years and 2 little boys. He blacked my eye after a fight and then i caught him on the phone with a girl, so I called it quits. I started dealing with a co-worker and in Dec I found out I was pregnant. I had never gotten pregnant on my own before (had to take fertility meds because of PCOS but i had gastric byp and lost 120lbs)and was leary about getting rid of it but I did on new years eve because me and my husband were talking about getting back together. Anyway, back with my husband and pregnant again. I think its my husbands but until I get an ultrasound I wont know how far I am. I been stopped seeing the other guy because I found out he was getting high off crack. So im keeping the baby regardless but I don't if I should tell my husband. I know every child is a gift no matter how it gets here and we can definitely give it a good life. Im 28 and my kids are 4 and 2. We live pretty well and I forgave my husband for alot he has done to me. I cant get rid of this one because Im scared I wont get pregnant again. This guy is not all bad he works and is so sweet, he just has a habit that I wont deal with, especially around my children. What do I do?