Girls looking at my crotch?

OK, here is some background information. I have been on a diet for a month and have lost 15lbs in total. One side effect of my weight loss is that "down there" has gotten bigger than it used to be by an inch. Also, I'm more of a shower than a grower. I went to the park with a friend and these girls that he knows really well come down to where we are at and start talking to us. I was talking to one when I looked to my right and see oe of them looking straight at my crotch. I didn't say anything and she looked at my face right after. I just stared until she looked away. Then yesterday me and my same guy friend were at one of the girls' houses. I was standing and I looked at the girl and she is looking at my crotch! WTF?! I was wearing shorts both occasions. Why do they keep doing this. I think it is kind of a turn on but it is also really akward. Especially since I just met these girls.