2months ago got pain lower back right side with pain in right lower and center abdomen had urine and blood test&kidney us. all normal. what can it be?

Kidney stones likely: Although other things are possible symptoms very likely due to kidney stones. Ultrasound not ideal test to detect stones ct scan should have been done though if you donot have symptoms anymore you may have already passed the stone. If blood in the urine and pain are persisting please make sure to follow up with a primary care physician or urologist.