you didn't say anything about actually wanting to be engaged, just that people you know are doing it. wait until you actually want it for yourself without the pressure of keeping up with the joneses. if you think your marriage will last if you get engaged/married soon, then the relationship will still be there if you wait. for some people it works out to get married young, but the reality is a LOT of people divorce ($$$$ even amicably) because you've yet to grow into your goals/personality
To put it one way, if you and he are really truly close, you will likely still be close after a couple more years when you’ve had time to grow. But if you feel like you have to hurry up and get engaged or else he might leave or get bored, or you’re afraid you will grow apart, it’s a sign to think about how strong the relationship really is.