<human>: Can you succinctly summarize the text in 1-3 sentences?

My bf and I have been together a good 6 months (living together for 5 of them) and we've been through quite a lot already. We love each other very, very much and I honestly do see a long future with him.
However, I'm only 19 and personally I feel like I have a lot of growing to do before I settle down like that. He pulled me aside and asked me if I was really committed to this relationship because it apparently had something significant to do with my v-day gift but he obviously couldn't tell me much more.
I'm really nervous and I don't want to just tell him "no". How do let him know that I'm not ready?
<bot>: Bf has been hinting he's going to ask me to marry him...I'm not ready and don't have the heart to figure out how to let him down gently.   :(