I dealt with a lot of similar things myself. Before I hit my head I could just sit down and write flowing prose without thinking of the technical aspects of what I was doing at all - the word choice, punctuation, sentence structure... all those components just seemed to come together on their own.

For several years after I hit my head, my brain just wasn't able to work that way. Each. Word. Came. Out. One. At. A. Time. And. There. Was. No. Flow. To. What. I. Was... ... ...saying. I'm sure you understand what I mean. Everything I'd create was still grammatically correct, but it took 3 times as long to write and came out SO sterile and uninteresting, I just didn't enjoy it anymore.

I remember one time at a party a bunch of my friends were doing this impromptu quasi-freestyle rap kind of thing, where someone would say a sentence, then someone else would add onto it with a line that rhymed, then someone else would jump in, and so on. Anyway, I was standing nearby and several people were saying "oh man, you've GOT to get in on this, this is so you" or something to that effect. So I tried, and I just couldn't come up with anything. Nothing at all. That really hurt. I'd always been known as a quick wit.

Fortunately, my relationship with words is one of the things that I've definitely gotten back (though it took a long time to get from where I was to where I am). I love writing again, and while I'm not quite back to where I can get "in the zone" like I used to (where I'd just type and type for pages on end without taking many, if any, breaks to think), I can see that I'm a much better writer now than I used to be when I compare pieces from then and now.

So yeah, you aren't the only one that's experienced what you're going through, and your "missing pieces" might well not be permanent. If it feels right to do so, keep the faith that you'll come back.