Major knee pain?

I am having some major problems with my knees right now. I have always had problems with them. I have what is called "backward knees" when I straighten them out they kind of bend backwards where there is a big dip between my thigh and lower leg. I have retaught myself how to walk to lessen the damage but my knees are really weak and hurt alot. For the past five years I have been in and out of braces and on and off of crutches. Here lately I haven't been able to wear my brace because i can't bend my leg with it and it slows me down which is impossible to do when you are chasing a 2 year old around the house. I have tried using just a support brace but it doesn't really help. The strongest pain reliever I can take is lortab because I am pregnant but I am still very much in pain. Sometimes the pain is so bad I cry and sometimes it makes me physically sick. The reason they are hurting so baddly right now is because I accidentally stepped wrong and my foot slid a few inches. Please help me