Does fiber make you gain weight?

2 weeks ago I started taking fiber because my doctor told me to. Since then, When I started, I weighed 188. This morning, I weighed 201. Is that a lot of weight for 2 weeks? I have been going to the gym every week day for the past month, and I am aware that muscle weighs more than fat, but seriously, 13 pounds? normally I just fluctuate 3 or 4.