Late period AGAIN!

This is the third time I have a period late more then a month! The first time I was late for more than a month was when I was 10 years old, the second time was when I was 14 years old, I was late for at least 4 months, and now I'm 20 years old currently and my period has been late for 2 months I went to difdrent doctors the checked me to see if I was pregnant and all test came negative and they also checked me viginally also not pregnant. Every doctor I go to tell me to go on the pill, I have it worked for like a year but it keeps happening. The times I do get my period it would be the worst pain in my life it's like someone is just cutting your insides out and I would barely be able to walk of how bad the pain gets. I will be seeing a doctor to see what's going on this time but I highly doubt I'm pregnant 😒 sorry for the long paragraph.....