Do you think being on birth control causes infertility?

I'm really not sure myself. Im certainly glad I've never been on it longer than 6 months (it made my emotions off the wall and major weight gain). I have read about studies saying it doesn't but most of these studies are paid, which means they are going to go in the favor of birth control. I just don't see how something that causes you to not get pregnant and can decrease your eggs be natural or good for your body. Especially over long periods of time. I also heard it thins you uterine lining which makes it more difficult to carry a pregnancy. What do you think? Does anyone have issues they think were caused by being on birth control? Specifically iud, pills, shots. Not condoms of course.