Before I continue, I want you to understand that I am not in any way criticizing you for choosing Mirena, although it's a shame that doctors, who should know better, prescribe dangerous contraceptives to women. Have you read the possible acknowledged side effects of Mirena? There are probably other side effects that are not admitted.
Follow this link to a page on the Couple to Couple League's website to find out how to plan your family in a way that improves your health instead of adding poisons to your body that sabotage its attempts to function in a healthy, normal way. http://ccli.org/nfp/contraception-sterilization/index.php
My husband & I have always used natural family planning when we were not ready for another child. It has been a huge blessing in our marriage, and I have never had to subject my body to the dangers of contraception. Contraception interferes with the closeness between husband & wife, creating a barrier between them, even if it's not technically a barrier method.
Ask your husband to read the side effects of Mirena and other contraceptive methods, then look at the Couple to Couple League website together (www.ccli.org), and see whether you're ready to try modern natural family planning, which is as effective as contraception but without the bad effects on your health and on your marriage.
Once again, I am not intending to be critical of others' choices, but do want you to know that there is a much better way available for you to plan your family. It's a blessing that you'll be grateful for if you give it a try. There are other NFP providers that are good, but I always recommend the Couple to Couple League because we learned NFP through them and are completely confident in the organization & the method.