hair pulling/scalp picking advice please

i've just found this site and in one way reassured that there are others with similar conditions but saddened that we are here in the first place. anyways my picking seems linked with my depressions, as in one triggers the other and not necessarily always the same way round. the depressions normally last 2 - 3 days, most of the time is spent lying on the bed staring at the ceiling and pulling at one specific spot on the head. i rarely eat or drink during this time and the picking becomes more intense to the point where i may try to actually push a pin or something sharp into the scalp, as a consequence there is always a bald patch and sore, not too mention a totally low self esteem etc. it feels as though there is something under the scalp and only pulling the hair can relieve it, but now there is no hair so i resort to sharp objects. anyone else experience similar, any advice?