Feel like a bad mother.

I feel like such a crap mom. My son is almost 9 months old and is just starting to get the hang of sitting on his own. He’s not crawling yet or any of the milestones he should be hitting yet besides he’s amazing at rolling and babbling. I feel like it’s my fault and like I’ve failed him because I didn’t do enough tummy time or exercises with him when he was younger. My cousins son is just a little older than my son and he is like almost walking. He’s also learning sign language and everything. I just feel like such an uneducated and poor mother. Especially compared to my cousin. She’s amazing. A great mom and works while I feel like I lack and am a SAHM.