31 weeks.. Huge jump in weight gain

Ariana • 36 pregnant with my second due 6/7/18
I'm trying not to weigh myself that often.. Every couple weeks, so I don't drive myself crazy. The whole pregnancy I have been steadily tracking to gain about 35lbs. I eat fairly healthy and excersize at least 4 times per week----From week 29 to 31 I gained 6 lbs!!!!!! I'm not even sure how that is possible! Has anyone experienced this!?!? Now I'm 31 weeks with 30lbs already gained!! Anyone else??