How to know if i have separation anxiety, or am i just clingy.?

Semantics?: It's not clear what distinction you are trying to make. One term (separation anxiety) sounds more "clinical, " one more informal, but they may well refer to exactly the same thing. Perhaps what you are asking is whether you have a problem that could benefit from professional help? If the problem (whatever you label it) is causing distress or affecting your functioning, then the answer is yes.