Unless you stop bottle he will not suck on breast, Sucking and extracting milk from bottle is easier than breast, you can use Ebm.

If your lactation is sufficient and the baby is hungry,he should be feeding well. Check for inverted nipples. No,don't mix them,give separately,but give top formula feed ONLY if your lactation is not sufficient. Give breastfeeds at a gap of atleast 2 to 2-1/2 hours,don't give anything else by mouth,don't wake him up for a feed. You,of course must take a good healthy balanced diet.