DT. Now.

From what I can tell, the only protein my hair can tolerate is AVG. I mix it with conditioner and apply it for half an hour (though I do think I need to adjust that timing a bit). It perked my hair right up and it's been great ever since. My daily products are all protein free. (Except the DCNoPoo and I use that sparingly and infrequently.)

For you, it could be that it was not protein after all, or it could be the one you used was not the right type for you, or it was just too much. Many people (me included) call this a hair 'journey' but many times it is more like a ride on a roller coaster!!!
remember, with all advice or suggestions for your hair, YMMV!!
My hair:
2b wavy, medium texture, low porosity, med-high density. Protein finicky.
My routine:
Cleansing: DCNP, every 4-5 days (occasionally use CJ cleansers).
RO: CJSC, occasionally use JCDC
LI: KCKT or CJSL
Gel: KCCC, CJCIAB for 2nd day hair (sometimes third)

Heat is my friend: warm water rinses, steam caps, and diffuse dry. I love CLU cloths and my Denman.