You aren't alone. There is a whole group of us who were old before we realized our hair wasn't poofy or frizzy or straight but doesn't dry straight. It's wavy. I was in my late 30's when I figured it out.
Your hair looks great and I give a +1 to the recommendation for protein treatments. Especially IAgirl's PT. Love.
(blog to help new wavies)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers