No Weight Gain at 18 Weeks?

Haley
I'm almost 18 weeks and still haven't gained a pound. I started off just a tiny bit overweight according to BMI but that was my "comfortable" weight that I've been most my life and I exercised/ate well. I've been mostly eating "clean" for my pregnancy, taking vitamins and drinking loads of water. I plan to ask my Dr. at my appointment Tuesday but was wondering if anyone else on here hasn't/didn't gain this far along? Some people I know say it's normal and some say I should be worried!