Terrified I have an oral cancer

This may sound really trivial but I've been having issues with recurring thrush in my mouth and now I have blood blisters all over the back of my tongue. My dentist told me to go back if were still there in 3 weeks. Tonight I've found a hard painful lump on my neck just to the side of my large neck muscle. I'm 40 and did smoke for 15 year. I'm terrified I have a mouth cancer.