I was 'diagnosed' at age 15 (I am 21 now) but felt the pain as early as 5. My prayers are with you and your child during this tough time. The reason I say I was 'diagnosed' was because the doctors said it was a fake disorder and it was just in my head. I am not one to let the pain get in my way to prevent me from doing anything however I know that I am suffering from severe pain all over my body. It is not arthritis and I have gone to many various doctors trying to determine what is wrong with me. I am hyper-flexible, have connective joint tissue disorder (whatever that means), sleep apnea, ADHD, was diagnosed bipolar before but don't feel it anymore, have a deviated septum, have weak hips, Patellofemoral Pain Syndrome, and then the doctors give up after awhile. I think they make stuff up to get me out of the office.
You'll be fine just keep your head up, get plenty of sleep and remember that everything you do will affect your child. I noticed that walks (as painful as they can be at first) are very rewarding over time.