Is it common to expect some weight gain after taking plan b? I took it almost 1 month ago, could it just be hormonal? I excercise and eat healthy.

Sure a bit. It is certainly possible to gain a small amount of weight with plan b. It is a type of progestin. Progestins commonly increase appetite and thus increase weight gain. It would not be likely to be significant in general. Definitely check a pregnancy test is this also can certainly happen despite taking plan b. Enjoy, good luck, and best wishes.