Ok ladies, help me out with getting my supply back

For 1 month I was EBF. I had a great supply. My son would eat and pass out he was so full. I would wake up shirt drenched. I needed nipple pads and got engorged an hour or 2 after feeding. 
When my son was about 6 weeks old, I decided to use formula on days I needed it. For example, I went on a road trip to see my brother and niece and I spent an hour on the side of the road in the middle of nowhere feeding because I never had time to pump, freeze, & bottle feed BM. 
I decided it was a hassle and it was leading me to be stressed and overwhelmed about leaving the house. I would always be late to places because my son had to eat. 
I started giving him formula about once a week when we had somewhere to be at certain times so that I wasn't rushing and scrambling to get both of us ready and him fed. I also have anxiety about feeding in public so there's that, too. 
Since then, I've stopped pumping all together and my supply is going down! I didn't realize it until today when my son skipped his morning nap almost entirely. He'd sleep 5 min, wake up and cry, repeat. I kept giving him the boob but he would get antsy and cry. He then began to scream and at this point my boobs feel flat anyway. 
I made him a 6 oz bottle of formula and he downed it in 10 mins tops. Poor baby was starving! After crying for 5 min I decided it's time to get my butt(or rather boobs) into gear. I'm currently pumping to get mynipples  stimulated since he had bottle. 
I find oatmeal and water help my supply a lot! But other than that, how many times a day should I pump? Once? I don't want over supply. When should I pump? 1 hr after he eats? 1 hr before he eats next??