FTM pain - please help

I'm 28 weeks and woke up this morning feeling really crappy (muscle aches, sore throat, shivery) but as the day has progressed I've started to get a lot of pain in my lower back (kidney area) and around my sides.

I phoned my midwife this afternoon and she told me to try a nice warm bath which helped ease the back pain at first, but twice now I have intense pain in my left side (and back) that lasts about 2-3 minutes and leaves me unable to move around. Has this happened to anyone before? My muscles are feeling achy already from whatever bug I seem to have picked up so I can't tell what aches are from being run down and if there's any that is more serious but this pain in my left side/back is the most intense pain I've felt and idk what it could be.

(I've not noticed any tightening of my tummy, and baby is moving around- just not sure if this is a normal kind of pain or if I should call up again?)