Lisa, truly there is no "right" answer to this. Only you and DP know what is right for you. If you feel that you don't need the test, then you don't. If on the other hand you would spend the next 5 months worrying about whether everything is ok or not if you don't have it, then perhaps you should have it. Some people choose to have the test even if they wouldn't terminate, just so that they could be prepared for an abnormality rather than having it "sprung" on them at the time of the birth. But it is a very individual thing. As you say you are at low risk being so young, so there is no need to have the test for any reason other that the fact that YOU think you should have it, or would feel better if you had it.

Good luck with your decision and your pg. I hope that your decision gives you peace of mind.