ex's mom doesn't know I'm pregnant still!

Miriam
I'm currently 36 weeks pregnant, I'm not with my baby's dad we broke up when I found out I was pregnant because he didn't want the baby. He said he would still be apart of her life but I don't know how true that is. He never asks me how the baby is or how the appointments go. I even tagged him in one of the first ultrasound pictures I got on Facebook (I think it was my week 15) and he got so upset with me and told me not to be tagging him in it and he untagged himself and blocked me because he said he hasn't told his family and he didn't want them to find out by a tag. That hurt me so much I felt like he was embarrassed of the baby. But anyways now I just found out he still hasn't told his mom I'm pregnant only his brothers know and I don't know why that makes me so mad! He said he was waiting until he got a better job to tell her so she wouldn't worry, I don't know why since he hasn't given me anything for the baby and I've bought everything myself or got as a gift at my baby shower. He's 24 btw and still lives with his mom. I'm so upset she doesn't know though and I want to go tell her myself but should I just let it go??