There are several ways to calculate when the second trimester begins. If you go by developmental stages, it starts at 12 weeks, 0 days. If you take 40 weeks and divide by 3, it starts at 13 weeks, 3 days. There are other methods, too, but it doesn't really matter.
In any event, I am 13 weeks and 3 days along today, so I feel that I can consider myself officially in my second trimester.
Many women look forward to the 2nd tri because it means that they will soon get a break from the nausea, but other than that notable food poisoning incident, I have not been sick at all. I suppose the hormone changes may give me a reprieve from my acne, which is still active, but not quite as explosive as it once was.
In the past few days, I have started experiencing some new symptoms: light cramps, some twinges in my cervix, and, most notably, shooting pains on the left side of my uterus if I stand up too quickly. These are annoying, but still relatively minor. Unfortunately, FB is still sick — he has a bad cold piggybacking off of his recent ear infection — so I don't get a lot of sympathy for my aches and pains.
I hope that the 2nd trimester goes by more quickly than the first. When I reflect on the fact that I've only completed 9 weeks since I found out I was pregnant, it seems that I will be pregnant forever.