feeling not ready

my boyfriend and I have been dating for 7 months I'm going to be 22 soon and he's 24. Ever since we first met we've had a very strong connection and feel like we were meant to be together. from early in our relationship he's told me he's going to marry me. now since we've been dating more he's been telling people he's going to propose and always jokes with me that it'll be not too soon but soon. and I've told him I'd be comfortable with dating for a year but when I say that he laughs and I know it'll be before that. I want to be with him but I feel not ready I still have a couple years left of college and I'm nervous becuase of the firsthand experiences I've had with a broken family and I've talked to him about all this and he says we can have a long engagement. I love him so very much he's like home to me but I'd prefer dating a longer time..any advice