On Medicines For Diverticulitis, Get Cramping On Sitting, Lifting Heavy Things, Eases On Standing. Reason?

i have had abominal cramps and some pain since the middle of oct.of this year,i had a fobt test done 2 weeks ago,a barium enemia done in march this year, and a colonspy done in sept of 2010,i have diverticulosis which now i am on cipro for,when i get up in the morning there is no cramps or pain ,if i put my legs up in the chair when sitting i get the cramping in my lower abdomen where all the cramping and pain is or if i lift something a bit heavy i get the cramping ,and i can be just sitting there and i get it,it seems better if i am standing,please answer my question