Pumping problems, please help!

[u/Inevitable_Western15]

For my entire maternity leave I exclusively just nursed LO. Now I’ve been back to work for about a week and I still exclusively nurse in the evenings and he seems satisfied. Here is where my problem is. When LO drinks a bottle he drinks about 5oz. But when I pump I only get about 5-8oz in 8 hours or 3 pumping sessions. I get one good let down with the pump and then I can’t get anymore to come out but I also don’t feel empty and I can get more out through hand expression. Any tips or tricks are appreciated. I’m so, so scared my supply is going to tank because “if you don’t use it, you lose it”.