I told my bf

I felt we have been playing at a serious relationship instead of actually being in one and he got really mad at me. lately we've been fighting over nothing and doing and saying things that are petty and going about our situations in an immature manner sometimes. i feel like we could act a lot mature and serious about the way we handle things and he says it's sad that i don't think we are in a serious relationship when i do it's just still so immature and needs work if we are going to make it anywhere near an engagement... am i wrong to feel how I feel?