Weird rashes on upper body and thigh, back

Ima try to describe what im going threw the best i can so you guys can get a better understanding of what im goin threw,i get these rashes on my upper chest,arm,neck,thigh,stomach,back,and some times they itch and sometimes they dont,but most of the time they do,the weird thing about these rashes is that they appear and then dissapear with in minutes especialy on my chest,and sometimes where it itches at there no rash there,they rash are blotchy but most of the time they appear in lines,i also get this lil rasied red dot on my arm but then it dissapears and wont come back till 4 weeks later,i had took a 6 1/2 month hiv test in may and it was neg,but i didnt start gettn the rashes till july so im still worried,i havent had sex since oct,so if u guys have any information of what this might be please let me kno and iam an afriacn american male.