While I am in agreement with those who choose to keep the details of their relationship a secret, I think it's time to differentiate when one's relationship is private and when it's a secret.  Keeping your relationship private is when people are aware of who you are seeing, but they don't know anything that happens within the relationship.  Such as what the two of you do when you're alone or when you are upset with each other.  This is very understandable seeing as nosy people are out for information to destroy. A really good example of this is Kerry Washington and her husband Nnamdi Asomugha, we know they are married, but that's about it.

Now keeping your relationship a secret is when everyone appears to be shocked when they find out the two of you are together.  Granted, you don't want to be that couple that floods Instagram timelines with lovey dovey pictures, I just think there needs to be something that makes it clear who you are taken by.  This may not stop, but definitely limits the amount of people who may openly flirt with your significant other. Because people know.  

I believe that people are kept a secret either because their boyfriend/girlfriend does not want everyone to know that they themselves are no longer available.  Another possibility is that you are not the only person that they have "committed" themselves to.  If you are unsure on whether you are someone's secret, here is the only sign you need: they tell you not to tell anyone that the two of you are together. This one sign pretty much explains it all. It may include, no touching in public, no pictures of you two on social media, things of this sort.

If this describes your "relationship", the harsh truth is you aren't in a relationship.  I honestly don't know what to call it, but you know you deserve better, so please don't stay in this mockery of a relationship.  This is to men as well, because I know women can be scandalous, lol. Whoever you're with should be the type of person that points you out to their friends and say "that's him/her".