It won't stop. Your hair changes over time (in my case drastically). When I was young I had almost jet-black, bone-straight hair. Couldn't get a curl to stay to save my life. Now - at 23 - my hair has gotten a lot lighter with a red tint and super frizzy and curly. I used to get body perms to give my hair some life but I haven't had to do that in years now.

My niece has done the same. She used to have white-blonde straight hair that's now getting darker and curlier. My sister's hair has gotten darker with every pregnancy (used to be blonde, is now brown) and has gotten curlier as time goes on.

I have been told it's changes in hormones that causes it. I guess that's why mine (and my nieces) started changing after puberty? I know pregnancy does a lot to your hair also.

Mine is the same as yours. The bottom 1/3 is in ringlets. Even when I chop off about 10 inches (which I do every year) it's still curly. And, as it sounds like your hair chemistry in general is changing, I bet, even if the curls leave, all you'd have to do is use a little mousse, scrunch it a bit and leave it be and it'll get curly again.