Iphoto app

I recently updated to Yosemite on my MacBook which in turn updated iPhoto, so when I start iPhoto it opens up ok but then tells me it needs to upgrade my photo librar, then when I click on upgrade I get a box for a split second which says examining your library then th the app just closes down. So I have effectively lost all my photos, I know there in ther somewhere but I cannot see them, is there a solution for this problem?