Strange behaviour of skin. Turns red.

Hello doctors, I discovered a strange behaviour in my skin in August 15. Whenever I went to the gym my tummy area itched when I sweated and I saw it turned red but it went away within 5 mins. on its own. This pattern continued for some time. In around November 15 I had stopped going to the gym and I discovered that whenever I came out from a bath, strange red streaks appeared all over my arms, shoulders. They also went away in some time everyday. Later these streaks or rashes sort of appeared as raised edges on my skin of the arms, back, chest. Etc. In around January 16, I noticed that now it didn't matter whether I bathe or not. These symptoms started to occur at any time of the day including legs now. Whenever any pressure was applied on an area, then also these symptoms appeared. Recently, I saw that now I have a dry patch on my leg where these symptoms occur quite severely, very red and itchy. It has left a mark on that area of the leg. Its brown normally and turns red.