I Had Beautiful Long Hair For Years. I Used To

I had beautiful long hair for years. I used to wear it short but it was still luxurious. It has always been fine but I had lots of it. I went on vacation in July (I was in chlorine for the first time in a long time, that is the only different thing I can think of) & when I returned my hair was very dry. I didn't think too much about it and put a deep conditioning treatment on it. It didn't help and then my hair starting coming out in huge clumps when I combed it after showering and complete long strands were falling out as I walked. That has stopped now but I have about half of the volume I had before. I have had blood work done and have no deficiencies except Vitamin D. Help!