well this shit got deep real fast, but not sudden, there where hints at it, pieces of flashbacks, insights into his mental state, and now it all collapses beautifully, like a house of cards that was made so a single gust of wind could blow it away.
His problem isn't that he is scared to commit or that he doesn't know what he wants, he is scared that the world is like himself and that he is wrong about what he hopes the others think, he is scared that the others are also just to nice to say no, just like himself, that the others actually hate him on the inside and only want to use him for their own trauma.
Thats why the straight forward girl from the band was a good influence on him, cus he could be sure that what she said was tru and thats also why his mother is poison for him, cus in the past she was unstable, did things that he didn't know how to process and now he fears that everything is just her plan to have everything work out in her perfect little way.