First this is an iMac forum, when posting please be careful to post in the correct area so your post gets the attention it deserves.
Next read and execute the steps in iPhoto 6 and later: Rebuilding the iPhoto library
Finally why are you not backing up your computer?? That is absolutely critical and there is no reason to not be backing up to an external HD using at least Time Machine. This should be your VERY first priority!!!!!!!!!!!!!!
Thank you... I feel so stupid! I am new to Mac.. bought it in the States and recd no training (no time). I used to backup on PC.. don't know why I overlooked.
Which forum should I post in future, if I may ask?
If you have an iPhoto problem, the iPhoto forum. No need to feel stupid, you are new and just were not aware.
To learn how to use Time Machine please click Mac Basics: Time Machine backs up your Mac