Hellllpppp!! My milk production is going low..

My baby is in the NICU.... this happened with my first son he was in the NICU... for almost 3 months and my milk supply stopped... it started with a small amount... then it got to a bigger amount of milk production then it went back down to how it was from the start..... any tips on what to do so my milk production doesn’t just do like it did for my first born.... I pump every 3-4 hours.... I’m worried the same thing that happened the first time will happen again.... 🙁🙁🙁😢😢😢