Note 13 at Gal. 4:20: Paul does not regret the things that he has said to the Galatians, but rather the tone in which he had to say them. If he had been present with them he could have approach them in a more gentle way and possibly explained himself more completely. Paul longed to be with them so he could answer the questions he had about them.

The phrase "I stand in doubt of you" means "to be at a loss, to be disturbed" (UBS Handbook, p.107) or to feel helplessness about the situation. Paul was like a parent feeling very concerned about his children going astray (see note 7 at 2 Cor. 12:14, p. 1044).