What should I do??

So I’ve been in a relationship for 3 years and we have a 1 year old together.. I just found out I’m pregnant, I haven’t told my fiancé yet.. not sure if I’m gonna tell him at all! Little back story, in the past 3 years he’s cheated often, while I was pregnant and even up until the baby was 3 months old. Mainly texting and exchanging pics with other girls with fake phone numbers. Well the other night we got in a big fight and I left and went to a friends house, drinking and hanging out and for the first time I ever I cheated, the guy pulled out but it was on my highest peak ovulation day. I’m pretty sure this baby isn’t my fiancé’s and I don’t know what to do or say.. my heart is telling me to get an abortion cause financially I can’t afford another baby, I work full time 40+ hours and just got my real estate license, I don’t have time or a vehicle for all my kids (this would be my 4th) any advice ladies, feel free to shame me..I messed up!

The other guy said he will take full financial responsibility and take care of everything for me and wants me to keep the baby, But I’m just torn..

Dates:

sept 26 fiancé came inside

Sept 29 hookup but he pulled out

Ovulation was supposed to be on sept 29