Dull ache/pain right side below belt line where bladder would be. comes & goes. notice more when i bend over at times. urine clear. no fever. felt no lumps. ab ultrasound for kidney stones in may was ok. i strain when pooping tho. muscle? cancer?

Pain: Pain. Abdominal pain in right lower quadrant can be appendicitis, divertiulits, polyp, colitis, could be tumor radiation of pain from your back. Glad the ultrasound was normal, but it does not mean you do not have a problem. Ultrasound is good, but not definitive.

Likely muscle strain: If not improved in 1-2 weeks, I would go see my primary care provider. It will likely get better on its own.

Muscle, may be: Cancer, unlikely. The picture you described goes more with muscular pain, straining with bowel movement is commonly due to constipation,you had colonoscopy and ultrasound done, and that's reassuring. You want to have more exercise and healthy diet, best wishes