Herpes Zoster is shingles, and is the same virus that causes chicken pox.
It's not an STD.
Anyone who's had chicken pox can develop shingles. However, it's contagious to those who haven't had chicken pox, or folks who are immunosuppressed, such as cancer patients.
Zoster runs its course and then is done. It's not periodically contagious like herpes simplex is.
Did you have zoster in the genital area that you are asking about sex?