Ah, I relate so much to what you've said - I was saying something very similar to my T last session. I was talking about how great my support network is - I have wonderful, loving friends and family who care so much about me. I am so lucky to have them. But it's not enough. Sleeping with as many men as I could was never enough either. I want my T to hold me (or a lot more than that), because some part of me (wrongly) thinks that would fill the empty hole inside me. But it wouldn't. So what will fill the hole?
In terms of where it comes from, to be honest I think it's very often to do with our childhood and the love we needed but didn't get from our parents. It's not necessarily their fault - no parent can be perfect... I love mine, and they didn't abuse me or neglect me... But they left a hole