My mirena (levonorgestrel) was inserted 3/4/2010 does that mean its expired and can i get pregnant? last period 2/28/2015 lasted 3 days

Not quite...: There is no timer inside the Mirena (levonorgestrel). There is no sudden event upon reaching the 5-year mark. The chance of the Mirena (levonorgestrel) being effective is the same the month before expiration and the month after expiration (real life doesn't change that rapidly. One can just make an appointment to see about getting a new Mirena (levonorgestrel), within weeks or 2-3 months.