Hi Katie, I also lost the ability to swallow even water about 2-3 weeks into radiotherapy. Luckily I had a peg tube, so I was able to keep my weight up and keep hydrated that way.
Skp07, 2-3 weeks in was the hardest time for me, after that it got easier as I stopped thinking about what was still to come, and just focused on having the best day possible under the circumstances.
Hang in there, it will pass, things will get better.
Best wishes to you all