My trainer recommends using a lacrosse ball when a foam roller is too big. I need to go buy one.

I strained my back at the gym a few months ago (aggravated a chronic problem with my sacroiliac on the right side) and managed to make it worse while stretching. I think it was due to bad form during an IT band stretch that messed me up. I had pain alternating in my back and on the outside of my calf. The main thing that healed it was time (with very careful stretching and avoiding the weight training exercises that aggravate the SI joint).

I'm still having some back/hip pain at night, but I'm hoping that stepping up the foam roller routine with help with that.