I am so sorry you are having these problems, and i can understand you being very frightened by all this. It is very difficult to know if the mirena is the cause of this or not. However the Mirena information is that whist on Mirena, it does CAN abnormal pap smear results. Now you only had it out in March, so it is reasonable to think that the Mirena may still be in your system slightly and may be contributing to the condition and or the resluts. So another smear now would be a good idea, even if you have to pay for it privately.
I certainly would not be taking any form of hormonal contraception again anyway, because there is some eivdence i believe that the artificial chemical hormones in all these products may cause or aggrevate cancer.
I dont know much about treatments etc, but i would have thought that if they suggest surgery then go for that option as a precaution, as these things caught early have a good chance of then being sorted out properly with your system returning to normal in time.
I am assuming they will be giving you blood tests and scans etc first to see if anything else is going on.
This does NOT mean that you have cancer, simply that your body is in quite a state and that it may develop into it at some stage, through the abnormal cells that they have discovered.
Blood tests will reveal if your tumour markers are up or down and give a much clearer situation, so before surgery make sure you have all possible tests etc. I am sorry i cant offer you much other help. I do feel for you tremendously.
In the meantime, go on as pure a diet and lifestyle as you can manage. no alcohol, caffeine, chemicals, go very low fat too, getting your fats mainly from things like oily fish, a little olive oil, nuts and seeds. avoid saturated fats. And include as much fresh fruit and berries in your diet as absolutely possible, to give your system a good wholesome base with which to work, and give your body the best possible chance at recovery. Lots of water to drink too, and chamomile tea to calm you and help relax you, when it all gets too much to deal with.
There seem a lot of sites on your problem when you google. I have listed three here for you, but maybe a good idea for you to look at all the sites under a Google and see if you can glean more info. I do wish you every success and hope that the worst will be avoided. Thinking of you. XX