A few weeks ago, I experienced a shooting pain that went through my left testicle and up through my left abdomen, and it felt a lot like a cramp or sprain. It went away after a few hours and since then, I've felt a slight twinge or ache in my lower left back. It hasn't really been flaring up for a few weeks, but for about a week now, I haven't been able to get an erection. Help me?