23, without children, thinking about puting the MIrena IUD in...?

I am considering getting the Mirena put in on Tuesday as my method of BC. I am getting married in three months, never had children, never had a partner before, my fiance has never had a partner before. I hear a lot of talk about possible infertility caused by the Mirena and about Pelvic inflammatory disease (PID) causing infertility. I dont know much about PID, but is there any way that I can reduce my risk of getting PID? I would like to have children in a couple of years and really do not want to ruin my chances of having them. But the Mirena, for many other reasons, seems like the best choice thus far (progesteron only, thickening of mucus, possibly not letting me ovulate, low dosage, less mood effects, and the hormones do not have to be processed through my liver). any thoughts or suggestions?