Here's a revised version of your message that conveys your feelings clearly and respectfully:
"Hey [Partner's Name],
I hope you're doing well. I've been thinking about our time together, and I want to be honest with you. I don't mind dating you again, but I've felt really hurt in the past when it seemed like I was giving my heart to you, only for you to turn to someone else.
What I need from you is a commitment to be all in if we’re going to give it another shot. If you're ready to stop playing games, I’d love to explore the possibility of dating again.
Take care,
[Your Name]"
Feel free to adjust any part to better fit your voice or the specific situation.