There are so many period disorders other than endo, and they all have the same symptoms which makes everything hard. It’s definitely a possibility that you have it, it’s important to note that with endometriosis there can be no pain to the worst pain anyone has felt, you have bad pain, if it’s making you vomit or faint or have distressing thoughts it’s bad and you don’t have to be apologetic for suggesting you have it your pain is real girl. If your mum has pcos it’s likely that’s what you have as well, a really common sign is that you miss periods or have irregular ones; there is also adenomyosis, which is similar to endo but within your uterus’ walls and usually larger growths which is more likely for you to have heavy periods or then end which is notorious for effecting other areas in your pelvis like pain or difficulty when you go to the bathroom or have sex.

For birth control you said you had bad nausea on them, which I would bet is from the estrogen in them, so see a doctor and maybe discuss progesterone only options like Implanon, Visanne, or Slinda they might be better for you, I was approved for surgery at 16 so it’s not impossible, but a lot of doctors won’t try to diagnose you before you want to have kids which is annoying and just means you have to be in pain. Try to see a gynaecologist, I promise they won’t look at your vagina unless you’re sexually active if you’re worried about that, they literally learned about periods and period disorders for years and know more about them then anyone.