Red Rash

I’m wondering if anyone has had this. I have a red itchy rash in the crease of my leg (right where my underwear are) I’m guessing it’s from friction and probably not drying myself well enough. I’ve been putting polysporin and Vaseline on it everyday but it doesn’t seem to be getting better. I’ve never had it until after my boyfriend did. It may be a coincidence or could it be contagious? Wondering if anyone has had this