Suggest Remedy For Stomach Ailments

Having cramps in feet and calves past couple of nights, constipation for about two weeks. Wondering what may be causing this as A LOT has changed in my medical history. I was recently diagnosed with erythrocytosis (2mo), I have had 4 phlebotomies over the past two months and have been taking 500mg Hydrea every night. In addition I have a pinched nerve in my neck causing shoulder pain which the neurologist confirmed through nerve/muscle testing and a MRI, C5-6 and C-7 are the culprits. I just started taking gabapentin (300mg night) and will increase to double the dose in a week, I take 8mg odensetron when needed for nausea. What could now be causing this constipation and cramping? I drink almost 2 liters of water a day, get moderate excersize, and take docqlace twice a day to try and help with the constipation. Gas is also very frequent and sometimes painful.