Unexpected Encounters During a Drive

New Wrinkle
He sends a text and she goes to suck him off. It was as simple as that. We go to his place, follow him up to his bedroom, and get undressed. I’d stand back and play with my dick as I watch her blow him. Sometimes she would call me over for a closer view.
The first change was making me wait before going up. I still got naked and played with my dick, but I had to wait a little before quietly going up to watch them. She says they talk more when I’m not there. And she likes to talk dirty during sex. When I finally go up to see them they would have already started playing. Sometimes they would be in a 69 position with her on top. His hands would be spreading her ass and pussy wide open while her head was going up and down on his pole. Other times, she was kneeling on the floor between his legs.
For the next change, I had to wait in the car. This can happen at any time. If she gets his text while driving to or from a date ourselves, we have to change direction. When he needs a fast blowjob, she will tell me to leave the car running. Other times she will tell me to turn the car off. That’s when I know then that she needs her cunt licked and he has time to suck her off. Either way, when she comes back to the car, we continue where we were going as if nothing happened—except she smells like cum. I have wondered if that is what she wanted—To be out and smelling like a used whore.
I can see where this is all going and know that I eventually will have to wait at home while she goes to suck his cock.
But last night was different for a few reasons. He text as usual but she didn’t give me any instructions. We drove the 20 minute ride without her saying a word. He answered the door naked (like normal) and she walked behind him up the stairs. She pulled her tight skirt over her hips to show me that she was wearing the sexy panties that I had just bought for her—a pink lace, crotch-less thong.
I thought I’d be standing in my usual spot against the wall, but when we entered the room she told me to get undressed even before she did. I stood there naked. It was painfully obvious how small my dick is next to his. Then she got undressed. After sliding her new panties off, she hung them on my little hard-on as if it was a coat hook. I stood there with my hands behind my back while they played in every position. And after he shot his usual load on her tits, she took her panties from my dick and used them to wipe up all of his cum. When she was finished she said, “open your mouth.” I did as I was told and she stuffed the cum-soaked panties in.
I had to keep them in my mouth as we got dressed, and even during the drive home. She looked at me from time to time and asked if I could taste his cum. I could only nod yes.
When we got home she took them from my mouth and said, “Now put them on!” They were still sticky as I pulled them over my dick.
“Boxer shorts are for guys with real cocks.” She said. “You’ll be wearing panties from now on.”
I stammered that I don’t have panties. She replied, “I have plenty. Go in my lingerie drawer and start trying them on.”
So, one by one, I put on her panties and came out for her decision, yes or no.
“And by the way”, she added, “get used to the taste of his cum. You’ll be eating it from now on.
His texts are different now. His latest was,
“Hey Bitch-boy, did she buy you any new panties lately?”
I don’t know what they will want me to do next.
I only know that I’m a submissive Jerk off and will do whatever she tells me to do.