Switching shampoos...any ideas?

When I got pregnant the texture on my hair totally changed and my shampoo brand decided to change everything on me so I tried some different brands. First of all I found that the "tea tree oil" shampoo by Paul Mitchell was the best because I started getting allergic reactions to some items during pregnancy and this one didn't. Plus it is really natural so it helped keep my hair under control. I also straighten my hair everyday but it tends to get oily before frizzy. You can get it at Amazon http://www.amazon.com/Paul-Mitchell-Special-Shampoo-Conditioner/dp/B001OVQSJG but it is expensive. You can get a genric of it at Sally Beauty Supply. The other brand I tried was Nexxus. I am using the spit end one now to try it. I would go on their website and take a little quiz and it will tell you which type to buy.