The best thing to do is read, read, read and learn about taking care of your hair. There's lots of good information here on nc.com. You should also determine your hair properties. Here's a link to help Live Curly Live Free - Curly Hair Basics
Once you know your properties, looks for others with similar hair and see what they use (in signatures.)
Putting your hair in a bun may be the cause of both the loss of curl and hair. If you're pulling it back tightly, you're pulling out the curl and possibly the hair.
3a (Corkicelli), highlighted, fine, low porosity
modified CG, since April '07
CG since 3/11/08
HGs: Anything Sevi; Curly Kinks Satin Roots, Curlycue ReNew and Coil Jam; homemade FSG and okra gel; soap bars; UFD Curly Magic; Botanical Spirits Jellies, CJ Repair Me