need help

Hello! I am a 16 years old with hodgkin's lymphoma stage 2. I have been taking chemo for over 6 months and there is this problem everytime that I'm scared of. Around day 3 my tongue and teeth started hurting so much to the point that all my cheeks and neck are swollen. I can't eat or drink anything and I don't want any food pipe in my nose. Doctors gave jel and mouth wash but they make my problem worse. I have to go through that for like a week whenever I take my chemo. Is there any suggestion for me to have less pain? How can I prepare or make it stop?