You faked your amnesia to stop bella for getting you killed. You knew to much about her because you where a forced spy of her enemy. You got hitted by car because you ran away from her, one day you where in the hospital and luckily your doctor is you bestfriend and you begged her to make fake papers about you having amnesia. Bella did believed this because the fake papers where too real so she tooked it a chance and lied to you.

Do you remember me? You're my wife.