Buttock skin itching problem. Cm bck!

I have a weird skin problem in my buttock area. It's been more than 4-5 years i have weird itchiness in my buttock area. When i bath in the morning and wear my clothes, as soon as I wear the underwear and pant my buttock starts itching a lot. I have to scratch and sratch it a lot and I cant sit on soft surface like sofa and bike seat when the itchiness is active. I have to sit on solid wood base chair or plastic hard base chair. In the afternoon like 3-4 pm it gets normal. I don't get any itchiness bt i mostly avoid to sit on very soft surfaces. When i bath in the night I don't get any itchiness. I don't even feel like I have any itchiness in my buttock area. Bt i can't sit on very soft surfaces. Hard mattress I sit on. I have used more than 20 bottles of sapat lotion in the buttock area no improvement yet. I had got ring worm or kind of itchiness in my jock area 3 years back, at that time i had applied sapat lotion in that area. In just 3 days the itchiness was gone off and nvr cm bck