That is a lot of things to deal with at once. Retinitis pigmentosa, as you well know, is the overactivity of the pigment cells in the eye which can block or damage the cells that make seeing possible. It is genetic. It can found as a symptom of many syndromes as well. A syndrome is a group of clinical findings that occur together. There are several rare syndromes that include retinitis pigmentosa and other symptoms that can look like a muscular dystrophy (muscle weakness). Some have testing available, and some do not. There is also the possibility that your two conditions are not related. Genetic testing is available for some forms of retinitis pigmentosa, ALS (amyotrophic lateral sclerosis), and muscular dystrophy.
To determine if any particular syndrome is responsible for what you are experiencing and if any testing is available, I recommend that you seek out a medical geneticist in your area. A medical geneticist can be found through the American College of Medical Genetics.