Weird symptom: cold & wet behind my knee

Dorothy
Has anyone else experienced this or found a treatment? When my pants leg or skirt hem brushes up behind my knee, it suddenly feels very cold/wet, like a drop of cold water or a quarter brushed up on that spot. It's only been happening with greater frequency this week (I'm at 5 wks). Thanks! Will also my doctor but still working on scheduling my first appt,