Mirena is bad!

Ok, so I've had mirena IUD for 6 months now. I'm 17 years old. I'm a very energetic person who loves to play sports and just loves to hangout with fam and friends..well I was that type of person until mirena well atleast I think its the mirena causing the trouble. Symptoms? Well insertion wasn't that bad just like a bad period cramp. But a few days after insertion, I was having these weird episodes at night. I would wake up arund 4 am with an unexplainable feelin in my body. That went away in about a week. After that every thing was fine about 2 months in. I mean my periods were regular cramping was fine. Then, all of a sudden I started to get moody, then came the bad cramping, light headedness,sick feeling in the morning sometimes vomiting, tiredness, I basically just felt like I was deteriorating! I feel old. Don't wanna go out. School is getting hectic. Plus I have a 2 year old son if that isn't enough stress already. O yea did I mention the weight gain? I've gained 26 pounds in 6 months! I know in my heart its mirena. My doctor tells me otherwise. Should I get a second opinion? O yea for the last few days I'm having terrible lower back pain. Anyone else experienced these symptoms? Please help!