Hey there and welcome, I had a similar cancer though I'm a little older. My problem had been long term (by this I mean long term irritation and a few biopsies before being diagnosed) - the one thing I'm gathering from all this is that your cancer sounds very aggressive, which tends to be the case with younger people who get it. Hopefully you are being treated at a CCC. Your dr. Sounds very on the ball. radiation is not fun - read up on it and prepare for what you are facing hopefully you will not have a horrible time of it, but to be honest even people who do okay with it still have a hard time - compared to a lot of the horror stories I had heard prior to treatment - I think I did okay - and believe me when I say it was bad. not trying to scare you - just inform you.
Forewarned is forearmed. You should eat now - enjoy your foods - bulk up a little if you can food loses its appeal around week three and stays unappetizing for quite some time after (particularly if you are receiving the bulk of radiation to your tongue.)

On an up note you are young so hopefully this will help you heal quickly - if you have people offering to help get their names - you may need a little help with the kids. Towards the end you will likely have low energy and feel pretty crappy. Rads is cumulative so the first few weeks following treatment are often the worst.

If you have any questions or concerns we're here.

If they are talking chemo as well - then cisplatin is likely a reasonable choice - this requires a hearing test and you should also see a dental oncologist prior to beginning radiation and bad teeth will have to come out and you should have flouride trays made.

Best of luck - sorry you have to be here, but welcome,