At waist length, I'd first point to the weight of your hair pulling some of the curl out, as opposed to needing protein. If it's not already, layering it would probably help your curls bounce up a bit.
With your coarse hair and bad reaction to proteins in the past, I'd be leery of using them, especially if your hair isn't overconditioned. If you do decide to try it, I've heard coarse haired curlies have the best luck with very occasional doses of keratin proteins or silk proteins. Start light and go heavier if you need to, or repeat the light dose for additional protein if the first dose goes well. Good luck.