tips on gaining some weight?

Faith • ❣️young mommy to a little boy❣️ 18🙌

I'm almost 18, 5'4 & weight around 128-130. i really want to gain more weight but Everytime I gain a few pounds the next month it's gone. I work alot, so maybe that's why I keep loosing the weight? honestly the only time I was able to gain weight and keep it for a while is when I was pregnant with my son.😭😭 any tips on how I can gain a few pounds without it all going straight to my stomach lol???