Started around the groin. now it has shifted to my thighs, where pockets sit and also between the scrotum and butt crack. index finger size for both?

Need a picture: Without a picture, it is hard to tell but your description suggests a fungal infection. You should try keeping those areas as dry as possible after showering, swimming or after working out. You can try an over-the-counter anti-fungal cream and use it daily to see if the rash goes away. Ultimately, you should see your primary care doctor for evaluation and treatment or refer to a dermatologist.