Please help advise me on what to say or do!!

So recently my best friend and I have been drifting apart. He and I just don’t text, and if we do I have to always initiate it. Idk if he realises that it’s going downhill or it’s just me. Ive tried talking to him and saying things like ‘what’s going on why aren’t you texting me or talking to me’, but he just brushes it off and says he’s busy. He never talks to me when there’s more people than just us, but idk what that means. to clarify, I don’t have a romantic interest in him and I just really value him as a friend. Any advice?