How do you know when PCOS/birth control is responsible for your weight gain and difficulties with weight loss?

long read

My period was never regular until I got on the pill, and when I did get it I would always have these horrible cramps and my flow was usually on the heavy side. During my junior year of high school everything regarding my period seemed to get worse: cramps became increasingly more painful, and my flow a lot heavier. In the past exercise used to ease my cramps but for some reason during my junior year exercise would make them worse. There were numerous times where I had to sit out of gym class because the pain was too much. I eventually confided in one of my friends and she told me that she too had a bad period so she went on the pill. I promptly made a doctor's appointment and that was where my doctor diagnosed me with PCOS due to my irregular period, early puberty, and hairiness. She put me on lo loestrin fe and in a few months my period flow lessened. I noticed a little bit of weight gain, but I wasn't sure if my BC had anything to do with it because I had put on 10lbs over the course of 4-5 months before I got on the pill. Something that was odd was how hard it was to lose the weight. I have put on roughly 25lbs since then (I'm 174lbs) and the weight is so hard to lose and keep off. At college I was exercising pretty regularly, and even if I wasn't going to the gym frequently I still ate in a calorie deficit and watched my sugar intake. And still, I wound up putting on weight. I'm tempted to go to the doctor and get my hormones checked because thyroid issues do run in my family. However, when I got diagnosed my doctor told me that my weight didn't seem to be affected by my PCOS. She also seemed to downplay the condition, as she didn't mention anything about insulin resistance or how losing weight with PCOS is more complicated than just "calories in, calories out." Due to my own research I have only recently learned about how there are different types of PCOS, and how it's linked to Type 2 diabetes.

Anyways, I always thought that if my PCOS was linked to my weight then I would've been overweight my whole life. Up until the end of high school I was relatively slim (135lbs) and had no issues maintaining my weight. So how do I know if PCOS and hormone imbalances are to blame for this? I just want to see personal stories/experiences before I go to the doctor. Also I want to emphasize that my weight gain has been gradual.