I also have an IUD, but I have a lot of trouble with anything that produces a hormone, so mine is copper. I consulted with several other IUD users before deciding to get mine. Most of what I heard was similar from woman to woman so it seemed like a no-brainer. Since then I have had a period every two weeks, for 7-8 days. EVERY TWO WEEKS! Now there's a reason to be b!tchy!
The trouble you are experiencing sounds very familiar to all the issues I have had with every form of hormone-producing birth control I have used (several varieties of pill, depo-provera). I am not sure what other methods you have used and your experience with them, but at first guess, that's the thought I jump to. If you are not getting the results or comfort you expect, get that sucker traded in for something different. Your peace of mind is not worth the hits that a device intended to make our lives better is putting to you.
I also don't know how long you have given your IUD a try. Good rule of thumb is try for 6 months and decide, unless your misery is unbearable. For me, I am giving this lady one more month and then making a decision. On a side note, I was told by a nurse practitioner in my late teens to try takng vitamin B-6 when I feel all "out of whack". And boy-howdy did it change my life!! It's over the counter, inexpensive, helps with digestions and somehow regulates the "emotion-overload". Hope this helps!! A.