Can’t stop thinking about this

Hi all! My baby is 4 weeks old and on 90 percent formula and 10 percent pumped breastmilk. The main problem she suffers from is something coming up in her mouth which keeps on waking her up. I am assuming it is the acid or milk. She makes a really horrible face when this happens and gets really flustered. She possibly has reflux. But the thing which makes me miserable is thinking maybe the formula is doing this to her and if she had been EBF this wouldn’t be happening. The reason I am saying this is because the only two three pumped bottles I give her, I feel like she remains calm and happy after them and when I give her formula she gets this reflux as far as I have noticed. I am so worried because my supply is so low and giving her formula is really important! I am giving her Aptamil ready to feed bottles. I am so confused as to why is this happening? What will I do if she actually has a problem with formula milks and can only get better with my milk?😔😔 I cannot produce enough. Has anyone ever been through this? Can someone please give me some guidance. I would really appreciate it!! The guilt is killing me.😔