Sense of impending doom.?

I'm 20, and this has been going on since I was around 16. My mother has hypothyroidism, and my father was bipolar, depressed, and an alcoholic. I feel like I am dying all the time, and I can't move the thought from my brain, every time a I eat something that isn't easy going down I convince myself it cut my throat and I will die soon due to internal bleeding. Every time a joint pops in my body i'm convinced it's a blood vessel or something that just burst and I will soon die due to internal bleeding. I am always convinced anything that is slightly uncomfortable will somehow lead to my demise, and I can't make the thought leave my head even if I know it's crazy and non realistic. This feeling is made worse by smoking weed, I get paranoid so bad I start convulsing and crying, thinking that I'm dying. 2 instances in which I was sober I also felt that I was dying and led myself into hyperventilating. This is taking over my life, I don't want to feel so fragile, does anyone know of any disorders this might be?