Mercury, Virgo, 7th house using traditional astrology
I'm trying to get a firm handle on traditional astrology, but I'm finding myself stumped. In my own chart, Mercury seems to play a major role. It's the most well-dignified planet in my chart, in an angular house, and rules (possibly) three houses: 4th, 5th, and (?I think?) co-ruler of 7th.
My question is, how exactly should I interpret the placement of Mercury in my chart, specifically with reference to it's role as ruler of the 4th house?