Don't do it!
We have all read the books and got the advice from professionals that children develop at their own rate and that the milestone guides are simply just that. Guides. But of course, you should trust your instinct if you feel that your child development is significantly slower and go for a check up with the doctor.
But you seriously need to just chill out. It doesn't matter if your neighbour's baby started eating solids before yours, or their hair is longer. You are going to have so many issues in your life, PICK your worries carefully! For instance, my friend and I meet every week for a catch up while our children who are one month apart sit together and play. As I am trying to teach Hasouni how to crawl, her baby is literally trying to climb over my head. She already conquered my living room, and now wants to climb me as the next mount everest -and this baby is younger than Hasoun. I was starting to get worried and was disregarding the fact that my child was walking along the couch to get to his toys. After I put my mind to check, I have come to the conclusion that if my child is trying to learn how to walk, than I think he is okay ;). Apparently, my sister and I never crawled when we were kids. So, there we go.
If you start comparing the frequency of your child doing a peepee or a poo poo, then I think it is time to take a little nice coffee break. Alone.
I don't know why we do this. We stress ourselves even when our children are looking at us and they are smiling and happy. I think the thousands of books exploding in our library shelves on parenting and the millions of guides on the Internet are causing more of a paranoia than helping.
I went out with a group of friends and their kids to a nice breakfast a few weeks ago and I noticed that one mom was feeding her child food with a silver spoon and giving him tap water. I started comparing how I feed hasouni, which is always with a plastic spoon and cooled boiled water so I asked her how come she is doing that. She said to me, and I swear, it was the exact shake up I needed to just relax with all the guides we read, "oh, this is my second child." She followed by the book with her first child, and after that experience, she learned that children don't immediately fall into pieces when you don't do things perfectly 24/7.