I was on the pill for 16 years due to very painful, heavy, irregular periods when I was a teenager. I was happy that it worked well for me birth control-wise, but also wanted to be a little more natural and optimize my health. Also, I still had wicked PMS.
The pill can mug you of B vitamins and other nutrients as someone here already said. I've been taking B-Complex Plus by Pure Encapsulations and have been told by various health professionals that I'll need to take B vitamins for life because not only does the pill rob you, but changes your ability to process them in the future (I was told this during a free consultation with someone from Needs.com, not a doctor, not sure how valid it is).
I would HIGHLY recommend that you do a hormone panel with a functional medicine doc as well. After being off the pill one year, really nothing changed for me, periods stayed somewhat irregular, PMS still bad, etc. It looked like (based on symptoms) I for sure had estrogen dominance, which would have been consistent with taking the pill for so long. Turned out I didn't, and there were some other hormones that were out of whack. Without the panel I would not have known what supplements/hormones to take, where to focus my healing efforts, etc. If you can afford to do an overall nutrient panel, that would be very helpful as well, then you'll know if you a deficient in any nutrients.
Other supplements that can be helpful: Calcium D Glucarate (helps the body process your estrogen properly) and DIM (diindolylmethane - can help bring down excess estrogen). Integrative Therapeutics is what I recommend. Calcium D Glucarate also helps reduce breast cancer risk according to an M.D. I saw, he said it's very protective and loves it for everyone including men.
I've started taking 2g of borage oil daily, for the GLA, and believe it's helping reduce my PMS.
Acupuncture might be a nice addition too, if you can swing it.
At least I can report that I didn't have any severe, adverse reaction to stopping the pill after so long. Good luck! Come back and let us know how you do and what supplements you end up taking.