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.
CG since 11/2011
2c /3a F /Mii, low porosity

Spring Products /Routine:
Clarifying: Herbal Essences Tealightfully Clean
Low Poo: Renpure Luxurious Argan Oil
Co-washes: Suave Naturals Tropical Coconut or Daily Clarifying
RO:
Tresemme Expert Selection Perfectly (un)Done, Cure Care, Suave Tropical Coconut or Daily Clarifying
LI (if needed):V05 Kiwi Lime Squeeze, V05 Strawbery
Renpure Brazilian Keratin Straightening (old formula), Cure Care
Stylers: LALSG
PT: IAGirl's as needed