I have set up icloud on both my iphone 4s and my PC and turned on photo stream under the photo in settings. It was working when I first set it up, but the photos I have taken with the iphone the last couple weeks have not been uploaded to my PC, except for 4 photos out of about 30 I took. My iphone has been connected to my wifi network every day so it has had the opportunity to upload the photos. What can I do?