I am assuming when you said it's the same thing you've been doing, that in the past your hair didn't revert? If it did, then it's time to change things around coz doing the same thing expecting different results is kinda crazy. Now if it used to work before and just hasn't recently. it's hard to say why--but we still do need to change things around.
The first thing I notice missing is some product to keep moisture out. Some people find grease does a good job of that. I don't know what oil you use but it obviously isn't keeping moisture out of your hair. Many of us use a cone serum to keep moisture out...so perhaps you could add that. Also heat protectant are good to use when you use heat. I know some people don't use them, but I used them for the first time in 2009 and I will never use heat w/o them again. I got a very good flatiron job and there was no that smell one usually gets when one straightens hair, not during the flatironing, after or even when I washed my hair later that week. And I had no damage.
You may get some tips from threads on straightening:
http://www.longhaircareforum.com/showthread.php?t=431336
http://www.longhaircareforum.com/showthread.php?t=400194