Suspected Endometriosis

hey i’m 16 and for around 2-3 years i have been getting chronic cramping, can’t move for days because of it. also very heavy period and painful, tired for 3 weeks out of 4, nauseous around my period, migraines. it’s been suspected for about a year and half that i have endometriosis, i had ultrasounds and nothing was found so the doc told me to have a very high dose of the pill (and skip periods) and just told me to survive off that my whole life. i’m not sure if this is common for endo, someone i know also thinks i have it. someone able to help, i don’t know what to do next to help this??? thank you :)