Intermittent vaginal itch - is my partner unfaithful

My partner and I are living in different towns at present.  We see each other every two or three weeks.  About 4 days after I am getting a mild vaginal itch / burn feeling.  It goes again after a couple of days and there is not any discharge.  Its not something I have had before, and I wonder if its an indication that he is having sex with someone else during the weeks that I am not there.