If it is about the change of your username, theymos can do it but he has done it for only well established members before. Members that are having low rank may not be able to have that benefit. But even if you will have the benefit, it may take time. I remember how it took people like The Sceptical Chymist a very long time before theymos changed his username. But my advice is that you should not have such in mind until you ranked up more and become well established.
The OP said this about 2 hours before your post:
Changing my username wouldn't solve this issue.
It's pretty clear that it's not about the username, and since he doesn't seem comfortable sharing the issue publicly, he said he would like to speak in PMs. So, there is no point in repeatedly asking him what he wants help with. We should let the admin or a moderator approach him and find out his issue.