If this is your first real relationship, then it might be that this is the first chance you've had in two years to break free a little - test the waters, one might say.
You say you've been 'thinking' about cheating on your boyfriend - is this just you, daydreaming a bit to fill in the lonely hours whilst he's away, or do you really want
to have a relationship with someone else? I think you probably do know the answer to that, but you are testing the depth of your feelings by putting your thoughts into writing?
You say you still have feelings for a 'dear friend', but that your friendship with him never came to anything because you left your country. It might be that you need to resolve this unfinished issue before you can be clear about your feelings for your current boyfriend.
I hope you can work things out.