Hey,
Well I have REALLY dry skin under both my arms, all over my stomach, my thighs, my lower back and waist. They are dark patches (there almost black) I've tried lotion and vaseline Iv'e had this since I was like 10 it wasn't that bad it was just under my arms and a little bit on my stomach but 2 years later its getting WAYYY worse over the years. I looked on websites and a few said I was pregnant others said it was early signs of diabetes
If anyone knows what this is and how to fix it it would mean a lot,,
THANKS!!

Have you been to a Dermatologist about it?

It might just seem like dry skin, but as you said with the diabetes, there can be more serious things that can cause these symptoms.

I myself have a lot of skin problems, and am constantly battling them but after speaking to a dermatologist I have seen great improvements.
I was put on a cortisone cream as well as told to make sure I drink plenty of water throughout the day to help keep my skin hydrated.

You can try medicated body washes until you can get a doctors appointment. Try your local Pharmacy (Chemist) for a deep hydration body wash to use in the shower.
Make sure you also ask for one that is for sensitive skin, even if you don't have problems with that and always test on a small area first (inside of your elbows is good)