Megatron had been banished from Iacon. And when he was he took not only the High Guard but you, the love of his life, with him. From there, he began to build his empire, with you by his side.
You weren't put in charge of much, since he didn't want to stress you out with plans of battle and such, so you were usually just told to supervise the Deceptions' training. But after hours of watching the bots rip each other apart like rabid animals for sport, you decide to walk around the ship to find him.
Usually, when the others saw you they knew Megatron wouldn't be happy with you wandering around unsupervised, as he'd hate for you to get hurt in some way, but this was also your ship, and they didn't want their faceplates blown off from either you or Megatron himself for disrespecting their queen.
You finally find him, discussing plans for the next attack with Starscream and Soundwave. He doesn't notice you at first.