Blood flow often decreases due to the uses of contraceptives. I doubt that this will affect your ability to conceive at a later stage. You will return to normal menses once you stop with the pills. Also use of pads and tampons has nothing to do with it. However you have mentioned in your medical history that you are on homeopathic Thyroid medication. Thyroid often causes irregularities in mentrual cycle. I am not very sure of the homeopathic treatment and would suggest you to get a allopathic consultation regarding your condition.