Sounds like you need to have a talk with him ASAP. He may be stressed and that could be why he is acting differently. I would say that the best solution would to sit down and talk with him (not over the phone) and explain to him how you are feeling and that it is making your worry. If he reacts negatively point it out right then (not in a confrontational way) and ask him why he has changed his behavior so suddenly.
That is so strange. I understand why you would be worried. My bet is stress but I hope that you can figure it out with him and it isn't something more serious!
Re: sorry my sister stuck her nose where she did not belong.