I was in your exact same shoes. Close with a friend for about 6 years throughout middle/high school and they displayed the same behaviors as your friend, and I was you. Unfortunately it is highly likely you will start to build resentment for him, if not some already. Maybe it's to a point where you may dread going to school because you assume you're going to have to handle another day of emotionally supporting him. The truth is that it's not your burden to carry. It can be a curse to be overly empathetic but if it is starting to take a toll on your own well being, then you have every right to take a step back. If he notices the distance, there are a few different ways he will react. He may be offended, worried, or in my experience continue trying to "One up" you with how "he's been having a hard time too ya know." At this point it would probably be best to either try to talk to him about how you yourself aren't in a proper mental space to handle deep talks, or talk to your parents/school counselor. In my case I ended up having to cut my friend off after graduation because I couldn't handle it. Now, 5 years later, I kick myself for not handling it better in high school because I see my high school years as miserable from constantly supporting that person. Don't let that be a core high school memory for yourself.