
I always count the day of the first "show" as day one. I realise that it totally depends on breed, but at 4 years old, this would be way too old for a first litter for any of mine (I have my breed spayed at 4.)
If you do a search, you will find that many of us will tell you to throw the ovulation pads! Sorry, but they're rubbish. :-(
If you are determined to use them, please be careful not to scratch her vulva - they can be pretty lethal.