Some of my books say 13w is 2nd Trimester, some say 14w. I'm starting to think 2nd Trimester now as my mood swings are going, but I'm aware that the shorted my 1st and 2nd trimesters are the longer the 3rd will be, so I'm having up to 14w for the first, then to 28w for the second. I know it's silly, just I don't want to be in my 3rd trimester for aaaaages LOL.