You really need to get it removed. It's dangerous to your health to keep it in any longer than you already have. And how can you not have insurance? If you're in the US, starting in 2015, because of Obamacare, anyone who doesn't have some kind of insurance is going to be fined. It's supposed to be "affordable" health care so why didn't you sign up? Majority of countries outside the US have some type of socialized medicine and therefore are covered that way. In 2015 there's no excuse to not have insurance anymore no matter where you live. I suggest you get some insurance ASAP and get it removed because your health and well being are at stake.
The IUD essentially block your body's ability to release eggs- there are many IUDs that have no hormones that are just as effective as the mirena. Most likely you're eother spotting because the hormones have worn off and your body's going back to its natural cycle. But you could be having issues because of the mirena being imbedded. Obamacare didn't make insurance affordable for a lot of people so don't feel bad for not having insurance- I still don't have any. But you need to get it removed regardless- you need to find someone who will set up payments that you can make- good luck