I found out that my ex is still in love with his ex

I broke up with him 3 weeks ago yet we've still been in contact since and have hooked up multiple times since.

Last night we were chatting and it turned sexual... I mentioned that I consider him to be my #1 (stroked his ego when I know realize I shouldn't have). Stupidly I asked him who his number 1 was. This is what he said:

"I’d have to say “a”, man I tell ya very nice tits, ass had very nice curve to it. That pussy was IMPECCABLE. Head was a solid 8/10, but gotta dock points for being lazy on top. Oh my and the moans alone make me bust 2-3 times. Overall a solid 9/10"

So I asked if this "A" was his ex who he was on and off with for 9 years. He wouldn't answer, so then we got on the topic of said ex and I asked why he kept going back despite the cheating, lies, etc. He said:

"Long story short I’ve never truly stopped loving her, people have meth, weed, alcohol as there addictions. She’s mine and I’ve only ever been able to get rid of it for a year at a time if that. No matter what she’s done or said I’ve always forgiven her over time. But it is what it is and people don’t change and I know that but deep in my soul I know I can’t fully let her go"

So then I asked again, "is A your ex?" he said yes. I feel absolutely sick to my stomach. I KNOW I shouldn't have prodded because I kinda already knew what the truth was, but I can't get over the fact that he's still in love with his ex who did him so wrong.

He reassured me that he really liked me and wanted me to be the one... but I still have this nagging feeling that during our 3 months together he would think about her, think about her during sex, maybe even look at her socials...

I feel SICK and I NEED to go no contact with him but I can't seem to let go. It's pathetic