Being a normal weight puts you WAY above average. Less than 30% of women and men aren't overweight.
The average woman is 5'-3" 170 lbs that's a big girl. Since there is such a small amount of attractive women the competition for them is out of control. The likelihood that you're the girls best option out of every man in a 100 mile radius is slim to none. Just another reason why online dating sucks.
Measured average height, weight, and waist circumference for adults aged 20 and over:
Men:
Height in inches: 69.0
Weight in pounds: 199.8
Waist circumference in inches: 40.5
Women:
Height in inches: 63.5
Weight in pounds: 170.8
Waist circumference in inches: 38.7