<human>: Can you condense the text into a few key points?

So my GF works at a place that you need a permit (or fill a meter) to park with during work hours. A male coworker doesn't have a permit, so he will pick her up and use her permit to park with. I have voiced my disapproval with the practice before, but ultimately it turned in to the age old argument of "you don't trust me, you're jealous for no reason". So she continued to carpool. 

Yesterday she texted me saying she was getting a drink with coworkers and will be back soon. I didn't respond, and four and a half hours later she came back home. I was pissed and didn't really want to talk. She asked me how my day was and so forth. I gave one word answers. She knew i was pissed and didn't talk about her drinks with coworkers.

Basically I'm concerned that she may be unfaithful. She was married when I met her, so I know she is willing to cheat. With us it started with getting drinks after class. Is this guy a threat? How should I handle this? Am I just being an immature little shit? 

It is also worth nothing that things have been a little rocky/weird as of late. She won't get dinner with my family for no good reason, she used to always go when invited. I was on vacation for a week and she didn't contact me the entire time. She gave me a baby ultimatum (I need to promise her kids within three years, i told her idk maybe). We fight sometimes but not often.
<bot>: GF carpooling and getting drinks with male coworker. Relationship a little rocky. Am I paranoid for thinking she is being unfaithful or am I paranoid?