Sat on rough surface (driveway) and now have small red spots like petichiae on my butt where i sat. i get these when i carry heavy bag too on my arm or with tight pants around my hips... why. blood (r and w) normal ?

Petechiae: It appears that you have increased capillary fragility. This can be seen in vitamin C deficiency, taking of aspirin or anti-inflammatory medication like ibuprofen or naproxen, problems with blood platelets. If this is severe enough to cause nose or gum bleeding, urinary bleeding, consult a hematologist for evaluation. Otherwise try taking vitamin C and avoiding aspirin,ibuprofen,naproxen,etc.