Hi Bood,
Being that you have both decided to be in an exclusive relationship, you are not in the wrong for trusting her 100%.
No exclusive relationship can work without trust.
It can be very easy to get a bit paranoid when you are in a long distance relationship. You can’t always know what your long distance girlfriend is up to.
Hence, your mind can easily start filling in the blanks.
Unfortunately, your friend didn’t help matters by planting a negative seed in your mind that many people who are in long distance relationships experience.
However, your focus should be on making this the best long distance relationship that you can.
Talk often.
Meet as often as possible.
Have frequent conversations on when the both of you plan to be in the same area permanently and set that date.
Never lose sight of it.
Your best shot at making this long distance relationship work is in making sure that it doesn’t become a seemingly permanent condition.
At the moment, it has only been about a month and the both of you are still in the throes of passion.
However, the longer that this long distance relationship persists, the higher the likelihood that your fear that your girlfriend could cheat on you becomes all the more possible.
The most successful long distance relationships are the ones that started with a plan. Without a plan or direction, you are more susceptible to a long distance partner eventually cheating on you.