Pumping advice

So

Ive been losing my supply and im wondering if its bc of the way my son nurses now. Before he would take both sides during a feed but now he only takes one side at a time every 3-5 hours which means one side could be left uneaten for 6-10 hrs.

First q:this could affect my supply right?

So now since he would rather starve than take a bottle (i dont wana get into this.), i need to up my supply. Right now im pumping 20 mins on the side he eats after he eats.

Second q: should i change the way i pump? Like instead of just pump one side after he eats, pump both sides or something? And for how long?

I feel like my only option right now is bring my supply back ( which ive been trying to do for three weeks with no improvement now) so i really need a good pumping strategy

Sometimes im afraid to pump a side before he eats it bc i worry there wont be much when he wants to eat.

Please any advice would be great but i dont wana get into "how do u know ur not making enough" discussion