Constructive critique or contempt?

A lecturer at my uni criticizes me constantly. I find his critique very helpful, but it's like 90% of the time. But, despite that, he always finds time for me. How to see if his critique is constructive critisism or if I'm just getting on his nerves?
I would like to ask him for help with an application but kinda have a feeling it would disturb him and he wants me to stop contacting him.
Should I write him?