I have been trying to gain weight after losing too much. I eat very small meals every couple hours but the past couple days I haven't been eating every couple hours like I usually do and my mom says that I just have to force myself to or else my stomach will shrink again and it will be hard to get it back to normal again...is this true?

The usual size of my meal is either a sandwhich or a bowl of oatmeal or a handful of fruit/veggies