@arianalauria – More infomration would be helpful. How long were you eating 1900 calories? Why? What impact has eating 4000 calories had on you? Why are you considering going back to 1900?
If you’re doing any sort of ‘diet recovery,’ a calorie surplus is necessary for the body to repair and restore. Unless you’re rather small, 1900 calories is likely sub-maintenance, and would probably not serve you well. Here’s a decent calorie estimator based on several factors you can input and adjust. If 4000 calories feels like too much (if you have to force yourself to get that many calories down, for example), then you maybe adjusting to a mid-way point between 1900 and 4000 would work.