Abdominal Fullnes And Constipation : Gastric flu or IUD ?

I have had a horrible case of gas and bloating and stomach fullness in the upper region of my stomach. I haven't had very much pain, but the bloating and gas is just as worse. I have been constipated for about a week now and drunk down some Magnisium citrate two days ago. I haven't had a bowel movement since, is this normal? Also, my stomach doesn't feel so gassy anymore because before I could literally feel and hear my intestines gurgling and rumbling. I thought maybe I had the Gastric flu? But then I was looking online and saw that the Mirena IUD was causing a lot of these type of problems also. I have had a lot of bloating and gas for about a few weeks now, it got worse over the weekend, and now the gas seems to have subsided a bit. However, I still feel very very full and heaviness in the upper region of my stomach. I have had ovarian cyst in the past, one major cyst in which I had surgery. But I was fifteen and I don't remember anything but pain, not really fullness. Anyway..........Any thoughts as to what this might be would be dearly appreciated.