Breastfeeding and Formula Supplementing

FTM here...my son is just about 8 weeks and I've been breastfeeding since birth. But this morning for the first time I just can't seem to pump more than an oz or two at a time. My son is taking more than that each feeding. So I had to break out the formula we had stashed away so he'd have more filling meals (so I hope).

But is it OK to switch back and forth between BF and Formula like this? I hope to get back to EBF if I can somehow get my supply back up.

Thanks.