@sooooconfused,
Put a timetable on it.
There's just so long you can be a nice boyfriend about this. So make your decision. Will it be a year? Six months? The minute the communications begin to slow down? Something else? Just, pick something. Don't commit yourself forever. It makes you the schmo that she turns to when other options are exhausted, and it keeps you from following up with the cute girl at the gym who doesn't have so many damned issues.
And insist that your ex get some therapy. Moving back in order to confront her fears, etc., without a professional's backing, sounds an awful lot like an excuse to just bolt because things weren't perfect, or she missed her home. So at least be kind enough to suggest strongly that she get some needed medical attention for this.