How to end a longterm casual relationship with Scorpio man?

I met him at work. We didn't know each other, but the sexual tension was building up fast. We both were going through breakups. He with his 4 year relationship, and me with my 13 year relationship to the manipulative a hole aquarius. (Never again!)

Fast forward a bit, we finally get introduced to each other and start talking. We both weren't ready for relationships. So we agreed to keep it purely casual. The sex was soooo explosive and very addicting. We would meet up at your usual late hours, a few times a month. Two years later, we started breaking the fwb rules. We were actually dating without ever talking about dating. We hung out a lot at each other's places, cooked for each other, met each other's friends, had fun hanging out. But again, lots of things were still unspoken. I somewhat knew his ex girl was coming in and out of his picture. But I ignored that. I liked him and learned a lot from this experience. At one point I guess his ex girlfriend got into a relationship with a new guy and he was sooooo crushed. At the time, we finally had THE talk somewhat. He asked what I wanted, and that he didn't want to hurt me. He was willing to end what we have to spare me, and he was too shattered to give his heart to someone. I told him he never asked me for my heart and that what I do is my decision. And that I'm responsible for my own heart. I told him I was open for more, but felt I could handle myself to keep going. Even though I knew I was feeling something for him. Weeks later he started planning for us to go away for a weekend. I was excited because I truly believe in the potential of US. But I guess ex girl got out of her other relationship and begged scorpio man back into her life. From that point on, I never heard from him again. I knew what happened. Yeah it sucked and I really missed him. He crossed my mind every day, but I didn't shed a tear. I knew what I got myself into, and he never broke a promise to me. I moved forward with my life and felt I was going to be ok. I feel like the betrayal and major heartbreak I felt with my ex aqua man, prepped me to be a stronger woman....so I didn't let this scorpio wreak me.

Fast forward to 9 months later, I hear from him via text. We tried to meet up but it didn't actually happen until another 3 months later. In a way I feel like he's in the relationship with her still, but I still went for it. They're not married or engaged, so all's fair is my new motto. We slowly started picking up again on what we started years ago. But no we don't hang out anymore. Literally just those late night visits. The problem is, only now I realize I'm actually ready for something more meaningful in my life. Ready to find that next great relationship. I know it won't happen with him cuz I'm sure he will always love her and she's it for him. I'm over my ex aqua, I am not as passionate about scorpio (bit I do care about him a lot). If he were willing to give us a try, I would do it. But I know it's not going to

so I've come to this point where in my heart I know our time of fun has come to pass and I need to remove this distraction and focus on finding the one. Believe me it's hard, cuz he's so great in bed 🙂 and he is a sweet heart.. but it's time for me to settle down. My problem is, how do I start and how do I do it? I don't want to be mean, and I'm not looking for dramatics. Just one good clean end to 4 years of this on off thing. And do you thing he'd be down.for one last time? Lol