I think I like a guy from my college. We chatted a lot at a party a few weeks ago and he was flirting with me. I gave him my number and we have been chatting, but I recently found out that he has a girlfriend. When we chat, I get the feeling that he is interested in me and wants to get to know me better. He has also asked if I am comfortable with meeting him for coffee, but I haven’t responded because of what I know about his relationship. Should I meet him and see what he has to say? I feel as if I am doing something wrong by going out with him behind his girlfriend’s back. I don’t know if this is a sign that he can’t be trusted. What should I tell him?
You have nothing to lose by being honest and asking him a direct question about his relationship. At this point, all he is asking you for is a cup of coffee, which is perfectly acceptable because nothing says two adults can’t meet for a chat. If he does say anything specific that makes you believe he is interested in a date, call it out and ask him questions because you can and you should. You are under no obligation to accept going on a date with anyone who isn’t single, and you should point that out. If this still makes you uncomfortable, you can always refuse and explain why you don’t want to.

How can I stop comparing my relationship with the kind of relationship my friends have? It always makes me feel inadequate in some way, which is harming the way I communicate with my boyfriend.
If you know this is causing you both harm, and aren’t taking steps to address it, you’re part of the problem. You should understand and accept that no one other than the people in a relationship can comment on what it is like. All you can do is speculate, so why bother?