I have a painful ulcer on my vagina, does this automatically mean herpes?...i havnt had intercourse in months and all a sudden this ulcer popped up.

Herpes: Genital herpes is by far the commonest cause of painful vaginal ulceration. It develops for the first time a week or two after exposure. Since you haven't had intercourse for months, perhaps if you have a herpes lesion(which can be solitary), it may have been the herpes seen in cold sores that you spread to the vagina. Diagnostic testing can be performed on your ulcer if it persists. See your md.

No: No use in speculating about this. See your dr promptly. Begin with exam + appropriate tests to properly define what you have and what you do not have. Management naturally flows from that. If it is herpes it can be controlled. It could be many other things.