Help Calendar problems

[Blondiex10]

I have my calendar synced with my googlemail calendar, but yesterday I noticed that all recent calendar entries I have made (last month or so), and all past ones, have disappeared. The ones that remain have now changed to have:

Calendar: me@googlemail.com (correct)
Sender: me@gmail.com (where did this come from??)
Attending: Yes (???)

I am also now unable to edit these remaining calendar entries.

Any ideas?