For me, I've come to the realization that my hair does NOT like dry winter weather, perhaps yours could be the same? How often to you DT and how long do you leave it on? I find that homemade treatments work just as well if not better and there are so many recipes that you can tweak to fit your hair, and they are pretty low in cost if you use stuff you have at home. My hair loves the olive oil I buy to cook with mixed into my conditioner.
I also only use what I can find at my local target or grocery store as I am really trying to keep my costs under 10$ a bottle (for a good sized bottle). At the suggestion of another forum member I recently tried Yes to Carrots conditioner and I am having pretty good luck with that. Although today I am fighting a little bit of frizz that I think it was self induced.
What also helped was a homemade protein treatment followed by a deep conditioning treatment.
Also I know someone suggested trying some of the methods, but what methods are you using? Icequeen's method helped me get curl all the way to the root in my long hair and plopping for as long as I can has really helped me reduce frizz.
Saturday I was able to plop til my hair was mostly dry and I had almost no frizz at all. Today only for an hour and I have more frizz. I also found that messing with my hair is very detrimental to my style and just adds frizz. Which is also a good reason for me to plop as long as I can (if I cant see it, I cant touch it :P).
I agree hair can be super frustrating, I've only been working on a true CG method myself for 2 months and have briefly considering just chopping it all off (well not really lol).
The best thing that has worked for me is to just accept my hair for what its worth. I figure as long I keep my attitude positive, treat it right, it should eventually (I hope) fall into place how I want it to.