Cheating

So my high school sweetheart, who I’ve been with off and on for about the last 6-7 years, the weekend that just past I found out that he had been cheating on me since the middle of this year, and we are engaged and we have been expecting twice. 1st time we lost the baby due to stress and now I’m having a miscarriage again due to stress and just finding out everything that he’s been up to. And now he’s saying that it’s my fault because I didn’t give him any attention and I was too busy working. And he wants a second chance, what should I do?