dry skin... or something else... *tmi pics*

this big patch here showed up about 3 weeks ago and my mom said it is dry skin and so did my sister. then it spread as you can see. it's a few inches under my left boob. but wait. there's more 
it spread clear up to my tits... and yeah sorry that yellow thing is a hickey and I didn't mean to get a bit of my nipple in the pic. I took with the flash side so I couldn't really see what was picture was being taken... 
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any ideas on what this could be? 

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