Helppp I already gained 5.5lbs only 8 weeks.

Hi ladies,
Just wondering how much weight you gained in your pregnancies by the end of the first trimester. I am only 8 weeks.. 5'4" and I was 134.5lbs when I tested positive at the doctors a few weeks ago.. Just weighed myself after having a birthday and a ton of Christmas meals and I'm up to 140 already!!! 
I'm so discouraged.. I'm sure some of it is boobs since they have almost doubled in size and I had to buy a new bra already and some of it might be constipation but I just feel so discouraged.
Anyone else? How much did you gain?