I'm sorry you're struggling with this. It is normal to lose a lot of hair starting shortly after childbirth. While pregnant, the growth hormones prevent much hair from being lost, and then once the hormones shift after delivery, all that hair that would have been lost during pregnancy starts coming out plus the normal daily hair loss. Since you do say you have gray hairs since the pregnancy, it seems to me that you are experiencing at least some new hair growth. However, it seems like what you are experiencing is more severe than most women experience.
My first recommendation would be to talk to your doctor. As others have mentioned, your thyroid should definitely be checked, but there may be other underlying medical issues that are causing the hair loss. I think it's probably best to start with any possible medical concerns before turning to extensions or weaves which are actually likely to further damage your hair. Certainly vitamins and certain types of shampoos may be helpful, but I would definitely work on treating any potential causes as well.
Good luck!