I (23M) enjoys it alot when my gf (25F) talks about her past sexual experiences with her ex.

We've been together for quite awhile now. She is my first girlfriend ever and it has been a wonderful part of my life being with her.

Lately we met her ex during a flight back to our hometown. He was an older guy in his mid 40s now. He was seated next to us and we had a fun and great talk in the plane. All of a sudden, it hit me that unlike me... She had alot of experiences before.

So when we got home, she was unusually horny. And we had sex after a 3 month of no-action period. Then we just laid in bed and talk. I brought up her ex to her and asked her about him. She rambled on and on and on about him. I kissed her so I could finally talk hahaha.

And I asked her about her sex experience with him. The glow on her face was something I've never seen before. But.... She looked at me and told me to not get jealous. Then she explained it all in details. The things they've done, getting shared with his friends, his size and everything.

And out of nowhere, I feel a hard deep beating in my heart. Listening to her saying all these. I couldn't help but imagine it too... I cannot believe that I actually get turned on by that. Of course I didn't tell her. I was ready to go for round 2 after hearing all that. I feel really guilty for imagining it all.... But that night was the best night of sex I've ever had.

What do I do from here...? Why do I feel so guilty for imagining it all...and why the hell am I totally okay with it.

TLDR We met gf's ex on a plane, went back home, she talked about her sex experience about him, I got turned on by it. And now I feel super guilty.