You need to talk to him. You need to ask him what’s up with the other girl (without being vindictive), ask him why he’s been so distant lately, ask him what you can do to fix the fight you had, and ask him for validation that he still likes you.
Communication is always the answer, and even if it leads to a break-up, that’s still better than staying in a relationship where you have no idea what the fuck is going on.