What Causes Throbbing Sensation On Left Scrotum?

Last September I started feeling a sort of throbbing discomfort in my left testicle/scrotum and they kind of showed up in episodes and every now and then it felt like my pelvis was shooting some kind of juice into my scrotum and it would be heavy to walk around with and uncomfortable sitting with etc. Also since I was maybe 12-13 I noticed my left testicle has sort of a different texture than my right(not that there s a lump but it s sort of lumpy is the best way I can describe it, it s only noticeable when the scrotum is loose) but I ve had exams and it s never been mentioned(I m 18 now).So when the throbbing got more rapid and episodic and uncomfortable I went to see a urologist, got an ultrasound and they said I was perfectly fine, no torsion, but I did have a testicular bead (if I remember the term properly) but they said it was no big deal. So eventually the throbbing went away, only with the occasional throb every month or so, until today and the throbbing is kind of mild but still very uncomfortable especially when I have nothing else to think about. It s been lasting about an hour and it s starting to cool down. It doesn t look abnormally colored(if anything a slightly reddish hue but again nothing abnormal). I was wondering if I m maybe deficient on some kind of vitamin that keeps it normal or anything of that nature but mostly I was hoping somebody could shed some actual light on the situation instead of saying gimme a call if it gets worse. I apologize for the whole dissertation but I just want to be thorough and specific. Thanks in advance.