Demons in my head symptoms and conditions

Not really sure what to say here. Had my Mirena put in March 2007, 6 weeks after the birth of my second daughter. I had taken the pill before this, and twice I fell pregnant on it. I took it religiously, so obviously it just wasn't for me. I decided on Mirena, having heard many wonderful stories about it. I didn't find the procedure for inserting it painful or uncomfortable, but maybe this was because I had given birth such a short time before.
Shortly after having it, I began to feel depressed, and ever since I have been moody, irritable and quite hard to live with. I put this down to post natal depression, and my doctor was reluctant to give me any medication for it, his explanation being 'you've had a baby, your hormones are all over the place, you'll be fine'.
I came on here yesterday, a friend of mine asked me to research whether she could have the Mirena or not, she's got 2 little girls, the oldest just turned 2 and both were C-sections. Anyway, not to babble on . . ..
For the past few months, I've been living with demons in my head, I feel no energy, don't leave the house much, am totally depressed most of the time. My relationship is suffering, I'm very short tempered with my girls & husband.
I've thought about seeing my doctor to see if he can help with the depression, but now I'm wondering if this little piece of plastic is the root of my problems.
Before falling pregnant, I had lost 42lbs, abd I kept it all off during pregnancy through healthy eating. I came out of hospital 1lb lighter than when I fell pregnant. But In the past year, I've put every one of those 42lbs back on, and about 10lb more. I haven't been overeating, and I know I've not been 'dieting', but even after a few weeks of quite intensive exercising, this weight will not budge.
I am also hoping my husband will stumble across this page if I leave it on the pc, I really want him to realize that the 'raving lunatic' he's been living with for the past year or more might in fact not be me being the 'negative, bad person, but maybe that something which I chose to have inside me is the cause.
Now I'm at a point where I don't know what to do. Do I continue with the Mirena, or do I have it taken out? Can I live with the mood swings for another 3 years, indeed can my kids, can my husband? Or do I have it removed, and try find some other form of BC?
I would like to have another child or two in a few years time, so I don't want to do anything permanent, but I'm really in two minds on whther this 'coil' is worth the side effects. I have tears streaming down my face as I type this, tears of happiness that I've maybe found out what is wrong with me, tears of sadness because I don't know what to do .