What Are The Side Effects Of Iud?

Iam 20 yrs old and I have an iud(10yr method) since 2008 after I had my son who is 3 now.Between 2008 and now 2011 I really did not have use of it till about 4 months ago.Right after innercourse I have the urge to use the restroom but lately the thought of going is so painfull!It hurts so much is a burning sensation I have to hold on to the wall or the sink next to me.I then can barley walk and have to wait a couple of minutes for the sensation to go away!Do you think the iud has anything to do with it? I also feel a heart beat in my stomach when I lay down? What is this normal?