I have an 8-9 year old corn snake. She hasn't eaten in about 3 months.I feed her large mice and have offered it to her about every 2 weeks. Recently her head and neck is swollen! Sometimes her head is normal. Took her to the vet. He wasn't sure why. He probed her. He said he thought it was just air. Couldn't feel anything. Her mouth looked good. Anybody have idea what's up? I'm really concerned!!!