Just read through this thread and you won’t like what I have to say.
I think Hwcouple702 has given you lots of great advice but you don't seem receptive to any of this. You also don't seem to respect your gf a lot - I mean this senctence (which has also been quoted by another person in this...
OK, so my reco is not a specific hotwife/cuckold-movie (although there is an element of that in it as well), but it's a pretty good mainstream movie about swingers: "Swung" with Elizabeth McGovern in the lead.