I know you feel a bit wistful watching other people getting engaged because you'd like that too one day but really try to focus; focus on the fact that you are happy.  One of the biggest ways to screw up your relationship is to start comparing to other people when there's really nothing wrong with what you have, it makes you question things that shouldn't be questioned yet and create problems that aren't there.  

Just try to be happy with being happy right now, your time will come and if it for some reason doesn't THEN you'll have a problem to work through.  Let being happy be enough right now and trust you're going on the right direction.  If it is supposed to happen you will get there.