Re: Is it muscular dystrophy?
If you really want to know if it's MD, you should go to the doctor and get a DNA test. Yes, usually MD is inherited, but there are also random genetic mutations. Both my father, who passed in October of 2011 from MD complications, and my son have MD.
The most common indicators for one type of MD is large calf muscles, (even when my son was two people would come up and comment on how "strong" his calf muscles looked) tip-toe walking, frequent falling, (which you would start experiencing more and more right about your age) a wide gait when walking or hyper-extending the legs and foot, breathing difficulties, (later down the road) digestion and bowel movement problems, (later down the road as well, due to inactivity) and generalized weak muscles.
If these symptoms fit what you are currently experiencing, you should definitely get it checked out, but honestly before my son even walked I knew he had MD. It's one of those diseases that starts wearing you down from the day your born and continues to get worse the older you get. This is a horrible disease, and I hope you find out what you do have.