I am 23, and using Mirena. No problems with it aside from excessive bleeding (for about 5 weeks) in the beginning, and irregular periods. I have been on my period for 18 days (and counting). I am still having severe cramps, severe mood swings, depression, fatigue, anxiety, and back pain. What could it be, and what should I do?

You go to the doctor and arrange payments off the fees.
If you are in the US, there are various changes this year and more coming) so you need to look into getting insurance

You are having several of the side effects associated with Mirena, so it's important that you see a doctor right away.

Call your doctor's office and tell them what you are going through and also inform them that you have no insurance and ask to make payments.

If your doctor will not accept the payment plan, you may be able to get into a local clinic or urgent care that bases the payment on your ability to pay.