Hi Pat-
I am 4 weeks out of radiation and I'm having trouble with a lot of foods too. Everything has to be room temperature, and I stick to poached eggs and top ramen(noodle soup). Milk burns my throat and I have to chase it with water. I didn't have a peg tube, because my throat did not burn as badly as a lot of people's. I'm still taking fast acting fenatnyl before trying to eat the noodles. Anyway, to your question, I noticed too that the first bite doesn't hurt but the second or third often does- I think it could be becuase your mouth/throat builds up a protective mucus coating on it when you are not eating, and when you take a bite or drink, it washes it off so you feel the pain a few bites later. Of course, that's just my opinion but I have definitly noticed it, for example at night my throat feels ok but if I take a sip of water a few minutes later it starts hurting. Like Amy says, Lidocaine is great too. I often use a q-tip and spread it directly on the roof of my mouth before eating.
Hope it gets better soon!
Mel