You may have Fibromyalgia! I have it plus Full body RSD!! I have r front of thigh muscle ripping and bleeding right now! It's terrible! But You I think might have fibro. I know when i first had it I felt like I had the flu ALL the TIME! Muscle pain, exhustion. Seek a Reumatologist!! Right away. Annie from Toms River Good Luck, Take Care!
One of the side effects of steroids can be low potassium and muscle cramping can be a symptom of that. The side effects of steroids are more readily seen when taken orally, however, I can attest to the fact that they do happen with injections also!
Try increasing both your fluid intake (dehydration can also cause muscle cramping) and potassium rich foods (bananas, potatoes, tomatoes, etc.) to see if this helps. If it doesn't, give a call to your doctor and see what they suggest or if they want/need to run a blood test to check your potassium and other electrolyte levels.
I hope you feel better soon!