[Cammo]

I grew tall really quick when I was going through puberty (all those years ago....) anyway, I have a couple of stretchmarks on the inside of both legs in my groin area either side of my scrotum. They aren't that big and are fairly unoticable but since I started going to the gym I've been getting bigger and the tops of my legs rub when I walk/run. It wouldn't be such a problem apart from the fact that it rubs where the stretch marks are and the skin being softer/stretched in these areas has given me real discomfort. Last week I walked for a few miles and they started getting pretty bad; It wasn't until I got home and had a look that I realised that they were rubbed red raw - I've been walking around with antibiotic cream & sterile pads stuck to my thighs since.
Is there any product (creams/lotions/powders) or even special underpants that can help prevent this happening again.
I was thinking of getting something similar to lycra bike shorts to wear under my clothes but I fear they'd get all sweaty & uncomfortable.