What Causes Pain And Weakness On Replacing The Copper T?

I am 34 yrs old. Having one son (4 yrs). Last Monday I replaced my Copper T. After that i am feeling very weak, getting pain in my lower abdominal as well as in my lower back. Today I showed to the gyneac. She prescribed some more medicines like pain killer, anti biotic for 5 days (though last week i was on antibiotic) and a multivitamin. Why, in the second time I am having so much of pain and weaknesses?