For the past month or so I've noticed what feels like a small lump or swollen tube underneath my right testicle where the epididymis and vas deferens are (not actually on the testicle but underneath it). I'm not sure if what I'm feeling is the epididymis and vas deferens or something else because I can feel the same sort of thing underneath my left testicle but it is nowhere near as big. The strange thing is it seems to be more prominent when i am erect, and the right testicle seems to stick out a bit as if the lump is pushing it upwards.

Is it possible that the vas deferens, epididymis or other veins around there could be more prominent or swell up when erect? Ive examined myself in the shower and everything feels normal but as soon as I am erect the lump seems to enlarge and get harder..

Thanks in advance for any replies!!

P.s i am 18 years old.