Old Prostitutes Buttholes Wide Open

I had my first sex experience when I was 14 and it wasn't with a girl with my age.
Instead, I lied about my age and paid a prostitute that didn't seem to care how old I really was.
This experience obviously wasn't long, as I didn't last more than 5 minutes and nutted almost immediately as soon she started to ride me.
After collecting enough money, I go to the same prostitute and this time I managed to last around 15 minutes.
I did this 4 more times and the last one was with a older woman, as she was the only available.
She knew that I wasn't old enough to be there but money is money and good for business.
It was nothing like the other ones, and she really cared about me not cumming and made small pauses to ensure that. Needless to say, I ended with a big smile on the face and feeling like "A man".
I'm 18 now and I'm obsessed with having the maximum amount of sex with older women, preferably 50+ one's, which I pay most of the time for it.
Yes, I have a girlfriend and we have sex regularly, but I'm always thinking that I'm fucking those older woman most of the times and my girlfriend hates being on doggy position because I stretch her ass in such way that I always hurt her.
The older prostitutes that I normally search have big asses that I love to stretch just to see their buttholes open when fucking them doggy style, and this makes me get so hard that I once kissed the prostitute ass that got her completely surprised. I'm so obsessed on older women with big asses that now I pay to fuck their ass every now and then just to stretch those asses and look at the wide open buttholes that I love seeing and sporadically fuck.