Hi! I Have Recurrent Shoulder Dislocation In My Right Shoulder

Hi! I have recurrent shoulder dislocation in my right shoulder since 2010. I was diagnosed with chondromalacia in both knees in 2013, and now, after my son became 6 months old both my knees and shoulders started to hurt. I took care of myself and had no problems with my joints since 2014 until my 7 month of pregnancy (this year in 2018). I want to get back to working out, but my muscles get tensed really quick. I have an appointment for an MRI for my right shoulder and I might need a surgery. However, I would like to know the cause of why all my joints started to feel weak.