Red very itchy Rash on lower legs (insides) slowly growing upwards

I (37, M)visited Cedar Hill State Park in south Dallas on Memorial day weekend (5/30/2010). We spent about 5 to 6 hours by the lake. We grilled some chicken and played around, but did not enter the water at all. After returning, we all (my family and other two families) started developing red rash (slightly bumpy) on lower legs, mostly on inside legs. My wife and two daughters (4 and 8 yrs) had these rashes all along ankles, and I had on my inner calves and knee area and some on thighs. THESE HAVE BEEN PRETTY BAD ITCHING, especially at night. It has been more than 10 days now, and everybody in the family is developing new spots all over the body every day (on the back, shoulder, groin) I even got one itchy rash today on my penis and damn, it itches the worst. My PCP has no clue what's going on. Had not been able to get good sleep for last 10 days. Hydorcortisone cream and Benadryl don't seem to help much. PLEASE HELP....