"you are stooping so low" means your behaviour is below the moral level of acceptance, (this is a verbal form of rebuke)

It must be "stooping", which originally means that you are bending your body forwards and downwards. I guess it means here in this sentence that you are depressed.

* stooping. They are similar however stooping is a result of you own doing, mostly in your control. E.g by shouting [back] at a drunk person you're stooping low. Sinking on the other hand may be a result of other factors surrounding you, usually out of your control and sometimes emotionally. For example stress.