I pulled a leech off my leg back in 1990 or 1991 in the 19 Mile Bay area of Tuftonboro. I wouldn't be too concerned. They are common in NH. Probably because they are nocturnal, most people don't come into contact with them. My experience was the result of walking through a portion of the shoreline that had a good layer of the previous falls' leaves along the bottom.
Here is a link to a DES fact sheet on leeches in NH.
http://des.nh.gov/organization/commi...ents/bb-10.pdf