Gaining not losing weight

Unless you have an underlying medical condition, your weight gain is likely coming from you eating more calories than you burn. Do you weigh your food with a food scale and log your calories consistently into MFP?

how long has it been?

have you just started or increased your workouts? if so your muscles may well be retaining water to repair themselves which is masking losses. this will flush out with time
http://physiqonomics.com/the-weird-and-highly-annoying-world-of-scale-weight-and-fluctuations/

are you tracking food and ensuring to eat at a calorie deficit or just working out? weight loss is done in the kitchen not the gym.
https://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1