Skin itching after bathing. This please.

I have been noticing that i have problems when i bath with normal water once all dried up i get bad skin itches & also if i itch it comes up with red patches ( I do use regular soaps like lux) havent had issues in the past have tried aloe vera soaps too however the itch doesnt seems to go away...also if i workout the sweat that comes out sometimes it itches sometimes it doesnt...i cant concentrate on my workout as well... i recently had Miliaria for which i was precribed medcines & lotion by a dermatologist i have completed the course howewer the itching doesnt stop after having a bath ...i do not understand what is the cause is it water or is it the soap ...Please guide what should be the next proper step inorder to cure this please ...Thanks.