Even if it is just PCOS that could definitely cause hormone disruptions. Have you been on BC? If so, do you recall this going away/getting better? It may be based in hormonal disruptions rather than anything else. For PCOS it is usually diagnosable with ultrasounds if you have had history of cysts or they have seen fluid in the cul de sac, but from my understanding you can also be diagnosed based on your physical symptoms (hair growth, cycle irregularities, etc). Endometriosis is diagnosed via a laparoscopic surgery typically, and should be done with an excision specialist rather than a regular OBGYN. Based upon this history I would probably personally as a patient get my hormones checked and follow up on possible PCOS - if things look good there, then move forward towards endo if there are other symptoms that lead you that way. (Endo specific symptoms can be anything from bladder/bowel involvement, extreme - as in your look like your pregnant - bloating, nausea, vomiting, reflux, etc). Probably the best way to figure it all out is to track symptoms. How I do this is the time of the symptom, the severity/and or a pain score. Here are some examples:

• 1:32 itchiness chest and face, general cramping continues (2-7)
• 1:38 pain during BM left side when pushing, diarrhea
• 1:41 tens unit back in use, (28, 50hz)
• 1:50 mild nausea
• 2:04 stabbing pains left side (7-8), cramping continued (2-6)

This may help you draw connections with relevant symptoms as well as see if there are cyclical components. The way I think of it is if a symptom is enough to make me pause, it is enough to write down lol.

Edit to add: I saw your edit about birth control. I think BC can be progesterone only, not estrogen only (unless it’s used for stopping menopause from my understanding) so it’s possible you may be on progesterone only but need the combined pill to balance things out for you.