Terrified I have cancer that doctors are missing

I am 33 years old and have been suffering with a achingness in my chest and back for weeks/months even. I have recently lost 2 stone i was active in the gym and eating healthy up until this aching got to me. I went doctors he sent for bloods and a x-ray and it was all clear he said the pain would resolve itself, however it hasn't and it has just got worst. My weight is maintaining although I'm eating the wrong foods and lots of it as i am now feeling drained and always tired, I mean to the point I'm doing house chores and it completely wipes me out that I have to sleep or lay down it literally takes all my energy. My aches are getting worst. I even changed my mattress, thinking maybe this was the problem, it hasn't made a difference if anything its getting worst. I went A&E on 2 seperate occasions they did more bloods, checked for clots and did x-rays! Everything on both occasions was fine. I went back to my doctor told him im tired, drained and my body is aching constantly. He sent me for a abdominal ultrasound test, that came back clear too. I am at a point i am crying out I am convinced I have Cancer and the doctor is missing this, I mean what else could it be im so drained, no energy my body is aching even my period didnt come this month and I am regular to the day! My doctor has prescribed different pain killers even gabapentin, none of which worked. I am do to have a endoscopy tomorrow, im hoping i get answers. I am convinced i have cancer though and im dying my body is aching and the last 2 days I've been so unsteady on my feet, I even nearly fell off the toilet as i went really light headed sat down. Im so scared I have my beautiful children and dont want to leave them. Its taken months with my doctor as I ring for an appointment and its a week before I get a telephone consultation (due to covid). Then he gives me a day to come in to see him, (thats another 2-3 days, so there's over a week just to see the doctor) then he order me to have bloods done, so I book for bloods there another week, then have to wait for results another week. All this time I'm getting worst and feel im being totally neglected. I ring up and tell the operator that I'm getting worst they tell me go to doc or A&E and then they tell me to go back to my doctors. Im really weak and tired and aching all over. Im getting worst. Ive told my partner I think im dying. Im so scared I just don't know what to do.