What Causes Delayed Periods And Cramps While On Mirena IUD?

Hi my names joanna and i've had the mirena iud for 2 years and a 1/2 and for the past 2-3 weeks i've feeling pregnancy symptoms like nausea, Headaches(which i think might be migraines), Bloated, tired, Dizziness, abdominal pain, frequent urination, and on top of that i did a kegel the other day and it hurt! My body feels really heavy almost like if i were about to faint. I went to the Monday May 23, 2011 doctor and explained my symptoms and she told me that maybe i had a bladder infection and she gave me some antibiotics. She told me she would send my urine to the lab just to double check that that was what i had. Turns out they called me the next day and they told me my urine had tested normal that in fact i did not have a urinary tract infection. Honestly i had not taken the antibiotics just yet so it was no problem. I'm scared i was really relieved that it was a urinary tract infection but turns out my relief just washed aways! I felt the exact same way as when i was pregnant with my daughter who is now 33 months old she'll be three in about 2 months. I've been wanting to take a hpt but i rather go to the doctor and get my blood the sooner i know whats going on the better! I'm really concerned if i happen to be pregnant , up until how many weeks can the doctor take my iud out before it is to late?