Swelling along with a sharp pain in my left testicle

hey guys this is my first post and I really don't know what to say so.......for the last 3 years I've been experiencing swelling along with a sharp pain in my left testicle  but it only last a few short minutes and then the pain will go away so far I've only had it when I wake up in the morning but it's been cutting into my sleep and happening at stupid times in the morning  I've been to the doctors about the problem but they said they didn't know so now I'm getting really worried   

If some one could reply to this it would be amazing .cheers