Next best thing syndrome

This is someone ,male or female,who claim to be in a relationship with only you ,but keeps you hidden from others. They do this is order to still appear single ,so they can continue to be sneaky on social media and dating sites. They will tell you they are a private person in order to not acknowledge your relationship with them publicly. You will never meet their family or friends .In reality, they are hiding multiple relationships with the opposite sex online .
These afflicted with this syndrome are usually a narcissist ,who tends to be loud , attention seeking, sneaky,and constantly plays the victim role to gain your sympathy . They are also selfish, entitled, and always thirsty for compliments and praise from multiple people in order to feed their fragile ego.
When you get suspicious and confront them about their behavior ,they will gas light you.
They will double down on the lies ,even after you present evidence of screen shots of said lies. They will move onto the next best thing, because they sense you are pulling away from them . Once you end the relationship ,they will quickly , generally within days , go public with the next best thing, in order to get one last dig in.