I have gone through your problems.
If you are ovulating and menstruating normally, you need not be worried about scanty menses. If you are changing two pads on first day and then one pad on subsequent days, it is OK. You are saving your own blood. You need not worry. If the bleeding is only spotting then that denotes some adhesions inside the uterine cavity
. Please get your x-ray of the uterus
done with radio-opaque dye instilled in it. That will reveal about the adhesions inside the uterine cavity.
Also please get ultrasonography
1. Knowing the thickness of the uterine lining. Get it done around the ovulation. It should be around or more than 10 mm.
2. Ovarian picture to see whether there is any bleeding from the ovary during ovulation. Your history suggests so. Also we would understand whether you have many cysts in the ovary.
If you inform me about these facts, I can guide you further. For that you will have to ask me a direct question. Go to my profile to find the option. Till that try to overcome the pain by some pain killer like paracetamol
I hope you will take the proper action and report to the Gynaecologist.