Feeling like a bad mother because of sons development?

Don't worry so much about development, and don't let anyone make you feel as though you are doing something wrong. Babies develop exactly when they are ready, and you can not "make" them develop. The best you can do is to *let* them develop. If he has lots of floor time, and he has things that he finds interesting and stimulating, then he is fine. Let him go at his own pace. Seven months is not so late to crawl. My seven month old doesn't crawl either, and my first child did not at seven months. Just enjoy your baby, don't compare him to others, and don't listen when other mums would like to brag to you about how great their babies are.