Four neighboring signs in four different elements...That's Me...
You were only dating for 4 months and moved in together in that time? The problem is you moved far too fast before getting to know this person. From what you've described this guy could be a narcissist, a player, or just a guy who moves too fast in new relationships. What we do know is that this guy showed you his best self for the first 3 months (since it takes about 90 days for the honeymoon phase to end), then afterward he showed you his true self. Also since you two moved in together quickly, I would assume there wasn't a real conversation regarding your personal boundaries and house rules.
The good news is, yes the Leo you knew was more than likely real (so what you felt wasn't a lie). The bad new is, now that the honeymoon phase is over you are seeing even MORE reality. You saw the good side first and now you are seeing the bad side. Know you that when the Leo has a conflict with you, he will devolve into a angry child. This is a huge red flag. He KNOWS what type of person he is. That's why he is spreading rumors that you're talking about him behind his back. He knows that he's no good, so he's trying to get in front of that by reversing the script and gaining sympathy.
To be frank, you can't have a real relationship with this person. My advice for the future would be to take your time in your next relationship. Get to know the person before moving in with them. Lastly know that this Leo isn't mature enough to handle a real relationship. It's best to let him go.