Those with latch issues, I had that with my first and third, like I said before, the nipple shield may really help. Don't be afraid to try it. You can work on weaning them off when they are a little older. I weaned my third off of it at 3 months old - might have been able to do sooner, but really didn't want to worry about painful nipples again.
I would avoid formula unless it became absolutely necessary, I think that is a dangerous road when it comes to supply. It is normal for the supply to drop at times. With my second he was 2 weeks old and I could tell he wasn't quite getting enough and was really worried for him, but I just kept nursing as much as he wanted and my supply did catch up within a few days to a week - probably was a growth spurt. I would make sure you feed your baby at least every 3 hours during the day and allow for only one longer stretch of sleep at night if possible. Do remember, formula may not be the answer to sleep desires either. If your baby has any problems with formula, you may have more troubles than you did with breastfeeding. My mom had to go through multiple types with me as I couldn't handle them. Formula isn't necessarily the easy way out, as tempting as it may be.