Not fair

Why is it always the mothers who have to sacrifice their whole lives to care for the child after a break up? My ex dumped me while I was pregnant and since our son has been born he's been around him maybe 5 times and our son is 5 weeks old already. I told him yesterday when I went to get our son that he could see him more often and I told him I'm the one who has to sacrifice my whole life while he goes out living his life. I love my son but I'm the one up with him at night. I'm Changing all the diapers. I'm the one taking him to doctor's appointments. I'm the one who can't get a break. Yesterday he only had our son for 5 hours. I'm so tired and stressed. This is not how it was supposed to be for me. I did not want to be a single mom again. I am now a single mom of 3. My son was not planned at all and he's the product of failed birth control. He seemed so happy but I guess he wasn't and honestly had I known my ex was going to leave me beforehand I would have had an abortion (I was 30 weeks when he left me). I love my son I really do but I already had one failed relationship with my other children's father and didn't know I'd be going through that again. Dealing with heartbreak and a new baby is so mentally draining. He gets to go live his life and it makes me so mad. It's crazy how you can go from talking about marriage and buying a home together to being single like nothing.. I didn't even expect it.