If it isn't anything you are doing to physically damage your hair such as using heat, dying, using chemicals and it isn't due to any damage or products then I would also guess that it could be hormonal. Have you spoken to a doctor? Maybe you should.
Are your roots and new growth growing in curly?
In the meantime have you tried any serums and other such smoothing products to help with the frizz? Maybe you could try some while you are figuring out what is going on.
If you are worried about the damage you could be doing with the curling wand I'd suggest searching for some videos on how to curl your hair without heat, many women are using safe heat free methods to get really nice curls. Maybe giving your hair a break from the heat styling will allow your hair to grow in healthy and hopefully curly again.
Last edited by Ericachristina; 01-15-2013 at 08:33 PM.