Frequently I'll have my friends and family tease me, or ask questions about when my girlfriend and I are going to get married. Sometimes, they'll even make these kinds of jokes to me while she's around, which is very uncomfortable and awkward. (I have talked with her about it, and she finds it uncomfortable too)

In my opinion, asking a question like this is extremely inappropriate because it puts us in an uncomfortable position without a good answer *regardless of how our relationship is doing currently*. 

For example, if everything was going great, and we were planning on getting married soon, this question is inappropriate because we haven't publicly announced that we're getting married, and it's none of their business. Or if we were going through a rough time, or had no plans of ever getting married, it's *still* inappropriate because it assumes that marriage is something we both want to pursue. (Note that I'm not directly saying either way where we're at because I think it's inappropriate regardless) I also think this question is very inappropriate because we are both pretty young and have not been dating for very long.

So I dislike this question because 

1. It's uncomfortable.
2. It's making assumptions about us and our relationship/plans for the future.
3. I feel like there's no good answer, and
4. it indirectly puts pressure on us to get married sooner.

If and when we ever do get married has nothing to do with anyone else, so no one else should be putting pressure on us to conform to their expectations.

So how can I respond in a way that

* Doesn't directly state anything about whether or not we are going to get married (saying *We'll definitely be married by such and such date* or *We're not ever going to married* both seem like bad options),
* Makes it clear that it's none of their business, and that I find the question uncomfortable, and
* Isn't lashing out or overreacting at them for making a harmless joke?

We live in the United States.