I am in my early 30s my current 5yo GF is in her mid 20s, first two years were great after that things started to slow down but only took a turn for the worse in the last year, she became more religious, feminist and less complacent.

I come from a rough place, low middle class, always excelled at school and got a scholarship to the best private college in my country. It was painful there, money is really important if you try to bang anything good in a private university. Didn't have much luck until started working on me (lifting, approaching, making some money) eventually got some luck and started going out on dates regularly.

~2 years post college, I met this young 18 yo, and we clicked immediately, she became my GF I ditched all other plates, from time to time given I am quite talkative I would still flirt with a girl here and there, at a business trip or at the gym never anything more than that.

Last year, my GF started her masters, some teacher started plating some stupid feminist ideas on her head, and they have affected the relationship, I really thought I was going to put a ring on her finger, but recently I am not so sure.

My GF is behaving worse and worse every day, I am focusing on my career and work, and sometimes I feel like she is dragging me down instead of supporting me like before she wants to live a dream life without much effort, her father has a lot of money that's why she can live like that, in the relationship I would say we split everything around 70-30. Still, she has become quite demanding she tells me about stupid stuff I don't really want to hear, she is constantly showing me her handcrafts or wants to watch a mind-numbing show on TV, I just can't live like that I don't have rich parents, every time I bring the topic she says she likes to live at the moment, and she is not good at planning.

I am not entirely innocent here; my old beta ways crept up over time, along with a health scare that took a mental and physical toll I got out of shape and started being lazy on some stuff. I still have to lose some weight, but I have been back at the gym for about 6 months now, I am playing a competitive sport again and this awakens a crazy sex drive again.

She is still very attached to her mother, I was planning a trip with her after even looking for flights she told me she was going on a 15-day trip with her mother to celebrate her 50th birthday. That really pissed me off, she went to the fucking trip while I stayed, just fucking working for what? Once a week sex, that has become less enthusiastic, to make money, so I can eventually support her lifestyle 100%...

She went to the stupid trip and out of boredom I decided to download a dating app, paid the premium plan to save time and remain as anonymous as possible, I was just trying to flirt some more and not shitting where I eat (gym, work). Got some matches, fucking apps are mostly bullshit unless you find a girl that recently joined, got lucky there, we started chatting, funny convo, asked for her number and went on a date.

I wasn't planning anything really, we went to a popular cheesecake place that is far from where I live, I don't live in a small city but still wanted to minimize the chances, I had a great time with this perfect tits 20-year-old girl with an amazing sense of humor. I had a coffee while she ate her cheesecake and could see her eyes glow every time I told her some crazy life story. It was still quite early that and next to the cheesecake place there was this almost empty bar and jokingly told her we should grab a beer, she was down.

Long story short, we ended up at my place, she resisted a lot but ended up sleeping with me, after morning sex we chatted a bit, she told this was her first time doing something like this she has never been with a man 10 years older nor have sex on a first date, based on the tightness down there I kind of believe her. I had one of the greatest nights in a long time, I sucked her perfect tits like an orphan calf, and fucked her like it was my last fuck. Of course, she is totally unaware I have a GF and while her body is slightly better I would still say my GF has a prettier face, still I can't get her out of my head.

GF is coming back from her trip tomorrow, I want to keep having fun with the other girl, but I am not sure how to proceed.

Should I be honest and tell her I have a GF? Maybe she is down to have some temporary fun
I am scared that I might be eventually caught, I am quite paranoid but still I probably can't see her as regularly and publicly
She has nothing else than my phone number, and I have a very private social media life, but I am still concerned that if she finds out my situation she might try to contact my GF.

Any advice will be appreciated.