It sounds like your trying to sync events that were stored on your iphone before you setup google sync..!!
If this is the case these events won't get copied to your google calendar..!!
To copy these to google you have to sync to outlook (for windows user) or iCal (for mac user) through iTunes and then export the calendar into .ics format for importing in to google calendar..!!As for events added post google sync setup not syncing there have been many people with this problem and i'm not sure why this happens..!!You could try deleting the google sync profile from your iphone and adding it again...!!