Some of the information in the curly girl book is out of date. To find info on the curly girl method I'd suggest looking in the newbies please read section of NC.com. This blog post is a great place to start.
Before and after the curly girl method pics
Post your before & After CG pics
The giovanni shampoo and herbal essence gel you use are curly girl (CG) friendly products.
Giovanni Tea Tree Triple Treat (GTTTT) shampoo is a non sulfate shampoo. This is good since it does not strip you hair of needed moisture. However non sulfate shampoo are not good at removing lots of silicones. Products with lots of silicones are shine serums, anti frizz serums and many moisturizing conditioners. Silicones end with -cone, -xane, or -conol. If you are using a product high in silicones, you may have silicone build up on your hair. This may explain where your waves went. I'd suggest washing your hair once with a sufate shampoo that does not contain silicone. Then I would try the CG method. This method does not work for everyone, but I think it is worth a shot. It worked wonders for me.
(a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers