Been trying to look after and grow nails after years of being a nail biter/picker. This is the longest time - nearly a year that I've achieved this. However my nails are awful and I'm not sure why. Thay are thin and bendy. Very flat with indents in. I don't put gel or acrylic etc on, just occasionally a sheer barry m polish to cover my nails when I get really embarrassed by them. Any ideas what's causing this and how I can have strong beautiful nails?