Headaches can come from many possible causes including an osteoma, so are you sure that is the cause?
It doesn't cause a behavioral problem so if you even have a behavioral problem, it is just a coincidence. If you are taking therapy for your anxiety then your therapist will verify this.
Who diagnosed you with an anxiety disorder? Before you faced this recent problem, did you have any anxiety problems or did they start with your discovery of this problem? That's assuming it is a problem, I have no idea what it is and haven't Googled for info because you're already seeing experts for it. I'm just commenting on the anxiety part of this, which is either an anxiety problem that has been there all along or it's nervousness and stress caused because you're scared about this condition and haven't yet received a proper diagnosis or treatment if any is needed. An anxiety disorder isn't rational, we're just frightened about things we weren't frightened about before for no reason. It's only a disorder when it's chronic. Everyone with a health problem is nervous about it to some extent until it's resolved or accepted. That's why I'm wondering who diagnosed you with an anxiety disorder. People with chronic ailments get pretty burned out over them and that can cause personality changes. I'm not sure what you have is actually a serious condition or just a bump on your head that's completely benign, I just don't know, but what you need to do is distinguish irrational anxiety from concern over something that will resolve once you get it diagnosed and fixed. One thing, though, the longer you stress over something the more it can develop into chronic anxiety if you let it and spill over into the rest of your life. If that's happening, therapy might indeed help you to figure out why you're so stressed over this. And one last thing -- those of us who do suffer with anxiety, and if that's you as well, we still get all the same life problems as everyone else, it just makes it harder for us to deal with them.