Iud's are weird

So about a year and I half ago I got the mirena. I had cramps and weird spotting for a couple months after getting it and then my periods completely stopped and haven't had any of the related symptoms. However in the last week I've had all the pms signs like cramps, acne, and sore boobs. Then yesterday I started having brown spotting. I was worried it could be a pregnancy so I took a test and it's not that. Also a few weeks ago I got a uti and was on antibiotics, but that all cleared up before any of this started. So my question, has anyone who has an Iud experienced a sudden change in periods like this and do you think it's something that could b potentially serious enough to see my doctor about?? Thankyou in advanced :)