Mucale Spasms in Shoulders & Neck

I am currently going to physical therapy for muscle spasms in my back next to my spine (right over from my shoulder blade) and run up into my shoulders and neck. Sometimes it it very hard to hold up my head because my neck and shoulders hurt so bad. Everything that they are doing in therapy doesn’t seem to be helping. I am currently taking robaxin (3000mg. a day)for this problem. Sometimes this helps and other times it doesn’t. Sometimes when I get up of the morning it doesn’t bother me, then as the day goes by it starts and just keeps getting worse. I have heard they laying on the floor with a tennis ball under you back on these muscle’s will relieve this. But I am wondering how safe this could be or would it just be damaging those muscle’s worse. I am in severe pain with this and I am unable to do anything without it bothering me. Any suggestions would be appreicated by my therapist and me. They are total dumfounded about how to help me.