It sounds like you might be having problem with your pelvic blood vessels. The sharp pain in your buttocks can be explained by it. Leriche Syndrome also commonly referred to as aortoiliac occlusive disease, presents with a triad of claudication, impotence, and absence of femoral pulses because of occlusive disease of aorta and it's distal branches.
Next Steps
get a dedicated Doppler done, ct angiography also might be required after a good physical examination by a ctvs surgeon/ urologist
Health Tips
you will require a panel of investigation as you are young individual having these complaints