Promise Me This

Was it meant to be? Or is love a big fat lie? Lexie Grey and Mark Sloan just broke up and nothing seems right. That's until they're both hit with some pretty big news. Could a bump along the way bring them together? Or tear them apart even more? (AU. Mostly Slexie. Some MerDer. Takes place after 06x14. This is how I wish things could've maybe gone instead)