How to increase milk supply?

My almost 11 month old has been exclusively breastfeed unless I am on an ambulance call or I coached(this fall and Spring), then she has a bottle. I had a 50 oz supply in the freezer and was keeping it up until I got covid back in January. I have been struggling ever since . I have 5oz in the freezer now and pumped for 30 min this morning before she woke up and only got 2 oz and that was with her sleeping from 10pm-8am. I feel like I have tried everything to pump more but nothing seems to be working. Please if you have any tips or suggestions let me know. I have a ambulance training Saturday that is at least 4 hours long and I am afraid I am not going to have enough in the freezer for her