Grrrrrr!

Have you started a new exercise regime? If so, it may be water weight. Muscles will hold on to water at first to help repair microscopic tears.
Are you weighing & measuring your food and logging it all? If not, you may need to tighten up the logging.

Chances are that you haven't gained 3 lbs. Weight can fluctuate up to about 5 lbs every day for so many reasons. You may have just weighed on a heavy day.
Don't give up. You can do this.