Well, good question about why would arms recover and then legs get shocks, or testicle in your case (btw I thought of Napoleon dynamite and the time machine ;)).. But, think of this.. Don't we always have some kind of health worry right? And once we 'recover' from something which was never a real issue, we find something else wrong with ourselves which turns out to be nothing wrong in the first place. So your arm was numb and painful which could have been simply sleeping wrong or lifting something wrong.. And it recovers.. And naturally types like us must find a new symptom to focus on.
I'll go TMI here too - I had muscle cramps under my belt line which I though could have been appendix, but then it spread to both sides, and while feeling around I got convinced my testicles were also cramping... Then of course tugging on them made it worse. I stopped eating sriracha and nachos for a day and left my testies alone and today I feel great. Was probably IBS.
Let your arm feel better, let your leg feel better, and instead of finding another thing wrong lets you and just take 5 deep breaths every time we have a new symptom, visit to site, and reaffirm that we're not alone in all this.. Then listen to some music and get out and take a little walk or water the plants or something..
I don't know it all, really. Not trying to sound preachy.. I'm in therapy so I'm actually trying to just share some of this tags I'm learning which are helping me...
And one more thing - trust your body to keep you healthy. Your body is once seriously complex and smart and powerful machine..