I just found out Im pregnant but my husband slept with a women 7 months ago what should I do?

My husband and I decided to make a big step in our marriage finally after 4 years and try to have our first baby. Well 7 months ago we went through a ruff patch and we both made our mistakes mine only being a kiss and hes being he slept with a girl when he had too much to drink. So we find out we are pregnant and decide both of us would sit down and let out all secrets, i told mine and I thought mine was bad but then I heard his and I flipped out, he cried and said he is so sorry and he regrets it, deep down i beileve it. Should we still have this baby or is it too late?