<human>: Note: Please forgive me if you spot any spelling or grammar mistakes as English isn't my first language.  

I'm 21(m) and my gf is 19. We are in LDR for more than 3 years now, but our relationship turned into proper one only 6 months ago.  One of the tutorials for people in LDRs I've found online says being overly suspicious when partner decides to go out for a drink or she didn't get back to you right away when you called and left a message is very unhealthy. Unfortunately it seems I fail in that point very badly. Quick example: she texted me this morning she passed an exam with B+ and she will get very drunk tonight with her uni friends. 
I'd like to react in this kind of way: 

"Ah, well. Getting drunk after passing exam you wasn't prepared to is absolutely al right! In fact, I would be drunk already not even waiting for the evening if it was me! I better congratulate her now and try to make her talk to me when she's steaming - should be fun, haha"

Instead, I'm badly stressed, full of anxeity and simply cannot get this thought out my head. It happens pretty much every time she tells me things like this. 
The other problem is contact with her. Recenlty I was good, but sometimes I just keep checking facebook and my phone expecting messages from her. In my opinion it's an addiction created because she's the only person I truly enjoy talking to. Yup, there's pretty much no one around me now. Lost contact with 95% of my friends, that doesn't help with the 1st issue either I guess. 

Before we decided to bind our future together I was fine with her going out, drinking or seeing friends. I'm not sure it is because I used to ignore her and didn't treat 'us' seriously or is it lack of friends and parties making so huge impact on me. And adivce you could give me guys? It's been waaay to long since I started suffering. I want to stop this and simply enjoy our relationship. If I don't get this sorted now it will become painful not only for me but for her too as she knows about the problem already.

Could you distill the essence of the text into 1-3 sentences?
<bot>: I feel really bad and stressed when my girlfriend goes out - the problem is I have to reasons to do so.