Breakup and pregnancy

Ok, so my ex SO of 14 yrs left back in Dec after Christmas. Now b4 he left we had been ttc for about 6 months. Nothing happened, not even a maybe. He would always ask me "why, arent we pregnant yet"... We have a 10 yr old daughter and his 11 yr old son and I are very close. We didn't speak much after he left he actually disappeared for about 3 months from my life and his kids.. he popped back up at the start of May. He would spend time with the kids, we would laugh, talk, he apologized but i knw he lives with another woman or should i say girl (19 yrs) old, though he still wont admit it to me or that she is his gf.. one night he stayed longer after the kids went to sleep. (His son was over too)and things got hot and heavy: sex, emotions, the works, for us both.. it only happened that one time. The next day i yold him it wouldnt happen again, he said he knew i would say that and he understands. We've been ok, since then except he wont come over. We talk almost everyday and he does see the kids.. but guess what i just found out... im pregnant.. smh i want to cry. Im happy and sad all at once. Im thinking about not telling him and just raising the baby alone... he is 31 and i am 28. We have have loved each other since we were 14 and 16 yrs old.... but it has been really rough.. idt there isnt anythumg that we have went through together both good and bad. I just dnt want any drama or lies while pregnant. Am i wrong fot feeling this way? I am scared shitless