I Have Had An On And Off Stomach Issues, In

I have had an on and off stomach issues, in the past two weeks, constipation, then I eat fiber and prunes and use vegetable laxative and then I finally go after like three or four days, then when I eat I feel Nauseated, I have had a headache and pain in my side...near the area where my gallbladder would be but I had it out a few years ago...I feel fine and then sick again
Could this be an infection of some kind?