I've had considerable hair changes since losing weight...it's incredibly brittle & dull, and the two times I colored it mid-weight loss really damaged it a lot more than it should have. I've had fine, thin hair ever since I hit puberty & PCOS made me lose so much during, considering when I was little, I had such thick hair!
One thing that I'm starting to do that may help you as well, is to take a Biotin supplement and I'm using coconut oil as a hair treatment as well, to try to encourage any new growth to come out healthier.
I have also used Biosilk on my hair which saved it back during a horrible highlighting mishap, to help give it a little shine, strength, & softness but I've heard really good things about Redken Anti-Snap leave-in treatment as well.