About three months ago, I had an unfortunate encounter with a man I didn't know. He rubbed his penis on my vagina, but that was as far as it got - I stopped him and sent him home before he could fully penetrate me. He had been rubbing against me for maybe 30 seconds if that at all. There was no semen and again, he didn't get his penis inside of me. Is there a possibility that I could have contracted HIV from him during this time?