will I gain weight??

I ate around 2300 calories for 2 days, now I am eating 2000-will I gain weight gradually on 2000 calsories?-because I weighed myself on my aunts scales and I had already put on 3 pounds!-Not in 2 days obviously-I'm talking about the week of eating 2000 calories. I've lost on 1800 before...so is this true or not?

If you were losing on 1800, it's very unlikely that you would gain on 2000 (that would require your maintenance to be somewhere between 1800 and 2000, and if that were the case, it would take about a month to see any change in weight.

3 lbs in a week (in either direction) is going to be water weight.