People who broke up because they felt too young, what happened?

I (21F) have been with my boyfriend (21M) for 2 years. We’re about to graduate and he’s talking about long term commitment, marriage, family, etc.

I’m starting to get scared that I’m missing out on some sort of crucial development by never being single in my 20s. Kind of a right person wrong timing feeling. I might be having a grass is greener paradox though.

TL;DR Has anyone ever been broken up with or broken up with their partner because they felt too young/felt like they needed to be single in their 20s? What happened?