I have most of the same properties as you (2b, fine texture, medium-high density, normal elasticity, normal porosity; density is how much hair you have while texture is the size of an individual strand of hair), so hopefully my advice will work really well for you. What definitely caught my attention about your hair is the fact that you've been told that you have fine hair. I was told the same thing although I though my hair was medium texture because it didn't act like fine hair is supposed to, but once I got a hair analysis, it confirmed that I definitely have fine hair, just a lot of it.
The reason that your hair is most likely frizzy on the canopy (the name for your outer layer of hair) but not nearly as much underneath is probably because it's the part that's most exposed to the elements (sun, wind, etc). My educated guess is that your hair needs some protein and moisture, possibly in the form of a PT and DT. Fine hair typically loves protein (my hair acts like it can't get enough), so you may want to try a protein treatment (PT) and see how your hair reacts to protein. You can either do a store bought one (they tend to be called Reconstructors) or there's a recipe for a fantastic one floating around on the 2's board (IAgirl's PT - really easy to make and a strong shot of protein). For a deep treatment (DT), I use GVP CB but there's many products you can use. Just make sure if you try either of these and your hair hates it, don't write them off. It may like a different kind of protein (it could hate silk amino acids, but love hydrolyzed keratin) or a different oil (it may hate coconut oil in the ingredients, but love grapeseed oil).
As to why your waves may be falling out, that may be due to your product choices. I have to use a really hard hold gel (Biosilk Rock Hard Gelee) and let my hair dry really crunchy to get any sort of staying power for my waves (I scrunch out the crunch once it's dry so I end up with soft waves, but I have to have that hard crunch. Another popular hard hold gel is Aussie Instant Freeze, but it's not quite as strong as BRHG. Plopping can definitely help your waves but you'll probably need a harder hold gel. Also, do you diffuse? That's the main way I really get my waves to perk up (I diffuse after scrunching in a 50/50 mix of Aussie Instant Freeze & BRHG) and once it's dry, I scrunch out the crunch and have nice soft, defined waves. Also, try looking up about sealing with oil, that helps with frizz. Hope this helps.
2b, fine texture, normal porosity & elasticity (CG as of 12/2011)
UFD Rich & Funky
VO5 Kiwi Lime
Tresemme Naturals, Aubrey Organics GPB, Ion Effective Care, MillCreek Keratin
IAgirl's PT, GVP CB
KCKT, Cure Care, CJ CCCC Lite
Curl Keeper, As I Am Jelly, UFD Curly Magic, CJ Curl Queen, TIGI Strong Hold Mousse
^^ day 1 of going CG; avatar = 6 months later