This hurts

I'm at a total loss and need help. I get the biggest and most painful knots in my back/shoulders and my lovely boyfriend rubs them out for me but it's gotten so painful and they constantly come back no matter what I do. Unfortunately, fancy massages are not in my budget. I'm an in training firefighter so I know caring heavy equipment is a factor. Does anyone know anythings I can do/try to keep them away?