Is oral herpes is an s.t.i or not? if not what are other causes?

Maybe: Herpes is a virus transmitted by contact. Oral sex could cause genital herpes to spread to the mouth or from the mouth to the genitals. This is not the only way to get oral herpes however...

Herpes virus: Oral herpes (hsv1) is most often from physical contact with an infected individual. Genital herpes (hsv2) is most often always contracted from sexual contact, and few cases have been shown of hsv1 coming from oral-genital contact, but the two are all but indistinguishable from each other. Maby the answer to your question is can you get herpes by not having sex, answer is yes. Just contact.