Hi.
Thanks for your query.
Noted your history of having a small red spot on the back of ball sack, its hard but not painful and you were wondering what it was? Your girlfriend had one on the top of her vagina exactly the same, and you both had sex hers is gone now, but now you have one. Both virgins before we had sex.
This simply indicates that you both are suffering from the same thing.
Your girl friends sebaceous
cyst has got absorbed by the body.
Now you have the similar sebaceous cyst.
But the sex has nothing t do with it.
I would advise you the following:
Since this is small and not
STD, just keep it under observations, do not pop and fondle.
This may resolve on its own or may need a small surgery to remove it.
Rest, you should not really be serious about it and stop worrying about it.