Hi, Beverly- this is one of those cases that needs a veterinary exam.  Biting flanks can be due to flank pain, stomach pain or ovarian pain; can be from adhesions/swellings/masses in the gut; can be just itchy skin or painful skin at the area of biting (or areas nearby that the horse can't reach)

The best thing is to get a reproductive and abdominal ultrasound done; minimal is exam and rectal.

Jaini, Merlin,Maggie, Gypsy, Eddy
BC09
EC mod/support