i have a bad(ish) back anyway and it flared up in both pregnancies. I like going to a physio to get exercises I can do for strength/alingment. I also find swimming and yoga or pilates (depending omn the injury) help a lot - keep mobility etc.
I have been having acupuncture lately and also cupping which works really well for me, I feel instant pain relief (whereas the others are more for prevention/longer term).
A massage is always good....