Help!

I just went back to work today and am trying to get a pumping schedule going for my 14 week old to have bottles during the day.

I pumped at 9am and 12:30pm and only got a total of 4oz each time after pumping for 15-20 minutes. I'm going to pump one more time at 3:30pm but I'm pretty sure it'll be a little less than 4oz.

I'm nervous because my guy has been taking ~4oz every 2-3 hours and I'm not getting enough for 4 bottles.

I've been drinking tons of water, eating oatmeal lactation bars and yogurt with granola.

Anyone have any advice? Baby has been getting 100% breastmilk so far.