I just realized this the other day: No matter what you do, the head of hair you have right now this second is as thick as it will ever be. You can make it look thicker, and you can make the individual strands thicker (lots of cones and henna and rinses, etc.) but thats about it.
I would suggest focusing on the hair that you are growing in right now. Protect the ends you already have, but make sure your roots don't wind up thinning out with them. Stretch your relaxers. Take hair/skin/nail vitamins to keep the hair strong coming out. Don't comb your hair too hard at the roots when you detangle or style, because it can break at the demarcation line and your hair will appear thinner. When its time to relax, only put it on the NG and protect the ends, because if you get any on the ends, even overlapping just a little, you are increasing the chance of it breaking off. One of the main reason my hair thinned out whenever I relaxed was because I was letting it overlap. I didn't suffer severe breakage, but I did notice my hair would be thick up until I relaxed and then deflate again. As soon as I stopped overlapping the problem went away.
ETA: But if you are looking for a quick fix besides henna and the other stuff I said, I would suggest that if you flatiron use bigger sections, and when looking at hair products dont use stuff that is targeted toward having sleeker hair, because it will make your hair look thinner. There are volumizing shampoos/conditioners that work. Finesse has a great thickening conditioner IMO but I forgot the name. I think it had Volumizing in the title
and to have beautifully thick ends.
