i'd suggest being patient. perhaps tell her that while you don't mind giving her space--her lack of communication has your imagination on overdrive and you'd appreciate her getting back to you on what the problem is. if she needs some time to work through it on her own, fine--but dropping a statement like that and then leaving you hanging is causing you a lot of undue stress and worry.
i would suggest not even trying to speculate on this--it could be anything from cheating to a missed period to her being abducted by aliens--who knows? and it may turn out to be nothing about you at all. maybe the problem is regarding her family, her work, her friends--who knows?
you can give yourself an ulcer over something that might be nothing, or, you can give her some time to get back to you. i'd vote give her some time
