Twin mamas, did you gain weight quickly?

As
Holy weight gain!! I was 169 before I got my BFP and now I'm 175. I haven't weighed this much in a long time and I feel like that's too much gain for 7 weeks. 
I work out 5 days a week and eat a really low fat vegetarian diet so I'm baffled.
 
Anyone having twins experience quick gains? I'm just trying to figure out what's going on. Maybe it's totally normal but I don't know. I've been reading I should only gain 1-2 pounds first trimester and I'm up 6 already!
I don't have my first appointment for awhile so I won't know if there's 1 or 2 in there. 
This is my 3rd pregnancy. 😫