Milk Supply and supplementing with formula.

I feel like lately my milk supply has been dropping and with my LO getting bigger he is eating more and I am afraid that I won’t be able to keep up. He’s 2 months and he’s just going to be eating more. I seem to pump 120-130ml (both breasts together) on average every 3 hours. I get the few pumps in the morning and later at night that are 160-180ml but with him already wanting 100ml each feeding. Last few pumps during the day I have only been getting 100ml and the odd 80ml from both breasts combined. I don’t know how I am going to keep up with him!? I have even been trying to pump more often but it’s just small amounts each time and my breasts are completely drained.

How do I get my supply back up? Is it possible to just lose milk?

Also is giving formula ok when you feed breast milk? I don’t want it to make him sick or gain more weight than what he needs to. Or for him to start wanting formula over breast milk. He’s 7 weeks 3 days old.