Multiple hard, swollen glands on one side of neck and head

I'm a relatively healthy 20 y.o male. For the last few months I've developed swollen lymph nodes all on the right side. It started out as one on the back right side of my neck that's the size of a grape, it appears to still be the same size. However I now have a cluster of multiple pea-sized lumps behind my right ear that I've developed over the last month or so. All my swollen glands are painless, hard and mostly immovable. I've been to an ENT who prescribed me antibiotics that didn't really help. I had to switch to a different ENT that I saw last week and he didn't seem concerned about lymph nodes and pretty much dismissed my concerns.

I have other symptoms such as migraines, widespread muscle twitches and dizzy spells. I recently found out I have a severely impaired thyroid and the beginnings of Hashimoto's despite being really thin -- could this be causing my swollen glands?

I'm really scared this could be cancer... My grandfather died of Leukemia around age 40 so I kind of wonder even though I'm young, it could still happen. I'm going to go back to my family doctor in a week to review my thyroid levels, what should I say regarding my swollen glands? It really concerns me that they are all on one side, painless, hard, didn't seem to respond to antibiotics, etc... this new cluster behind my ear is really scary too. Any suggestions are welcome