Ex sent me a friend request on Facebook

I'm not sure how to feel about it... I dated this guy back in high school when I was 16 and I was in love. I thought I was gonna get married and everything. I had to date him in secret because I grew up in an extremely religious household and wasn't allowed to date. I went to a private Catholic school and he went to the local public school. I would skip class to meet with him and we started having sex. I really did love him. But I got pregnant. My parents found out. Broke my phone. Made me cut all contact with him and home schooled me. I never even got to tell him I was pregnant. When I was around 7 months pregnant my dad got mad at me because I was mouthing off but I was just really hormonal and he threw me down the stairs hard. I ended up in the hospital with a severe concussion and also lost the baby. My mom told them I fell down the stairs and a CPS investigation opened up but I was forced to lie. I had my son cremated but my mom tried to throw out the ashes because she got mad at me and I ran away a little before my 18th birthday. I'm 26 now so obviously it's been a very long time. I've overcome the trauma caused by my family and live for my son everyday. He sent me this friend request and idk if I should accept it. He was a good boyfriend and I know he would have been a good father but if I accept it and talk to him do I tell him everything? I know we are supposed to leave the past in the past but part of me really wants to talk to him again.