Have your Dr test you for chronic fatigue syndrome, it effects lymph nodes, the way you described, off and on swelling, along with fatigue, Stress is a big trigger and causes flare ups. Also, how is your dental? sometimes bacteria can build up in the lymph and swells, I had that happen ended up having surgery to remove a few lymph nodes and was tested for Lymphoma cancer, it runs in my family, it was negative and ended up being caused from a bad tooth, infected. I think the best thing to start is ask your Dr. for a blood test for CFS, there is a specific test for it! Financially I know you are in a tight spot, check with your county and there should be a resources available for those who have no insurance or funds. where I live we have a place called Clinicas, and its based on your income, no one is refused treatment due to income. It is a sliding fee scale which can be zero depends on income. Check and see if there is one in your town. Wishing you the best!
So there are a lot of things that can cause these symptoms- you could have had a cold which caused sleeping issues and the lymph to be swollen. If the medication helped- I'd lean towards some kind of infection over cancer. Pain in your knees can be caused by so many possibilities too. It doesn't seem like these symptoms are anything to jump to a cancer conclusion about- is there anything else or some specific reason it has you worried that it's cancer?