I'm sorry you're having this anxiety, but it's perfectly normal after diagnosis. I was also stage 3. Though it's likely not cancer, you may want to see your primary who can recommend any necessary testing to determine why you're having this issue. I have to agree with carolinapam: If you have difficulty swallowing, it may be due to a thyroid issue. I developed thyroid issues (both hypo and hyper at different times) after treatment,and I have difficulty swallowing. Hope that helps.
Hugs & prayers,