Could be protein. Could also be glycerin or other humectants (especially if it's been worse with the cold). Could be some other ingredient that your hair just doesn't like. People are very quick to blame protein for any problems they have with their hair, but there are a number of ingredients that can cause problems for some people (some polyquats, aloe, just to name a few).
A couple of ideas for tangles: sealing with oil after applying LI, being very conscious of necklines and fabrics (I love turtlenecks in the winter but they're awful for causing tangles in my underlayer)
To test ingredient sensitivity you just need to read labels and try avoiding each ingredient one at a time to narrow down what's causing the problems.
3a/f/iii Before the chop- Donated to Locks of Love, January 2013
Modified CG since 11/5/11
CO-WASH: VO5 Vanilla Mint Tea Clarifying, DevaCare No-Poo
CLARIFY: CHS Treatment Shampoo (used prior to PT/DT)
RO: DevaCare One Condition, Regis Olive Oil
LI: Cure Care, As I Am Leave-In
STYLE: Re:Coil, Curl Keeper, Biotera Gel, Deva Ultra Defining Gel, GVP Liquid Sculpting Gel, Curls Rock Amplifier and Strong Hold Mousse
PT/DT: IAGirl's PT, One n' Only Argan Hydrating Mask