Bf immaturity

I have been dafong him for 2 years. He was my first bf mainly because every guy was so immature and when i met him he acted very mature, worked a good part time job in hs and was very motivated. Flash forward to today he is in college and i have never met anyone who acts so immature. My 8th grade brother is more mature and more caring. Is there any way to fix this? He says he love me but if he did he should act more maturr than he does. He has honestly reversed his maturity.