To Marry ? Or Not To Marry?

Ok me and my bf have been together for 2 years im 20 hes 22 and we recently got engaged he bought me a 11,000 doller engagement ring i was soo overwhelmed at the moment and there is no dout in my mind that i do care for him. I know my self very well to say that i know i want to experience my life and have good times with my gfs thats why i have this problem....he wants to get married within 3 years and the reality of it is i love him but i dont think i will be ready in 3 years even, i want to get my career lots of money in the bank and a house i planned on getting married around 27 just cause by then i feel i will know what i want. I just dont know what to do because he feels like just cause i dont wanna get married in 3 years there was no point in even being engaged and it makes me feel soo bad cause i have this ring on my finger that is beautiful and everytime i look at it i think of him and how much i love him i just want us to grow together for at least 5-6 years so we know what we want even in a year alot could change. I just need real advice from someone who is willing to give me some. I love him so much i just dont want to rush get married and divorce a year later, he doesnt see that, i would rather get to know him see if it will work out and if it doenst walk away keeping a friend not contacting my lawyer to get my ex spouse to sign divorce papers...how do i get it accross to him that its best to wait? without him thinking that all i want to do is party and we wont work out.......complicated yes