How i got to be fisted

Here it goes, I always wanted to fuck my gf in the ass , but it has been a difficult task,after a couple of times she said that if i want to fuck her ass again she would also fuck me in the ass with her dildo so i can see what it feels like.
One night i was very horny and asked her to do anal and she said yes , but first she's going to use her dildo on me . I sort of backed up but then she said she won't let me fuck her before she fucks me , obviously i gave up and presented my ass to her .
She said a good slut does enema before anal sex and she happily helped me to my first enema , How does it feel? she asked while she was fingering me , it feels ok I replied, and it did feel good even though I didn't want to admit it .
She got me on the bed , face up and asked me to spread my legs while she started stretching me with her fingers. I was moaning like a slut .
You little slut she goes , you're enjoying this , yes babe , she slapped my balls , my blood russhed to my head .
Mistress, im your mistress bot your babe she replied.
I'm sorry babe, slapp , I almost dropped a tear as she slapped my balls again . Yes mistress, sorry
Then , she started playing with her dildo , at this point i was face down and ass up .
This is not big enough , what do you mean I asked, i can still put three fingers around it , no way I replied, i want to see that . She grabbed a mirror and and I could see how her fingers and dildo we're going in and out of my stretched ass.
She then passed me the dildo and asked me to bite on it , why mistress I asked, because you'll need it she replied, ow put it in your mouth , at which point I obliged, seconds later , she said I'm going in
And i felt a stretch like never before and i was biting hard on her dildo , then i felt a easy that was quite orgasmic , thanks god she pulled out I thought....
Before I finished my thought. I felt something moving deep inside me and she said im all in , while she was pumping her fist in my wide stretched ass.
Im all wet she said as she pulled soacked wet fingers out of her vagina and put them in my mouth , without realising i was stroking my cock hard and came within seconds , my cum exploded from my pierced cock everywhere, part of it landing on my face and in my mouth .
She gently pulled her fist out of my ass and whispered in my ear
Now you can fuck my slut ass just like i did with yours , feels great doesn't it .