I'm not sure why you would admit your choice to drop your calories to 750 a day is unhealthy but also state that you think it's best. Would you tell your best friend to do something you know is unhealthy? Treat yourself at least as well as you would treat your best friend. You can't make your body the enemy and expect good results.
I read an article the other day that indicated that women suffering from PCOS see improvements when they add carnitine. Here is a link to the
article. PCOS is definitely a hurdle for you, but I think starving yourself is the wrong solution. Start looking at dietary changes you can make, and supplementation you can do, to improve your condition.
For example- WHAT you eat can often matter more than how much you eat. What does your diet consist of? Do you eat all whole, nutritious foods that you prepare yourself at home? Or are you eating nutritionally deficient processed foods? Do you consume sugar of any type? Do you drink soda? Juice? Do you consume wheat products? Many of the things that society has brainwashed us into thinking is healthy, or at least not unhealthy, actually is horrible for you. Many foods as well as "food like products" (processed foods) that we consume are highly inflammatory.
Check out the paleo or primal diets. Mark's Daily Apple (website) has some great info. Here are two success stories from women with PCOS that saw great improvement on the primal diet.
http://www.marksdailyapple.com/five-...ive-ever-been/
http://www.marksdailyapple.com/i-did...floor-with-it/
Don't starve yourself. Nourish your body with the foods it needs, and cut out the crap that's hindering or hurting your journey to good health.