It's not so much that using a teat would confuse him, but that his feeding is what's telling your body to make milk.
If he's filling his nappies well, that's great!
Mixed feeding isn't the great evil people sometimes say it is - but if you do a formula feed, then overall you're going to end up working harder to get things back on track. So, if it isn't medically necessary then it really would be better to avoid it (and that would only happen from about day 5 since he's got reserves until then - and your midwife would tell you, they're checking carefully for this).
If you mix feed, you're very likely to have to stop breastfeeding before you want to. And it really is worth fighting on: once it's established, breastfeeding is a wonderful experience for both you and your baby.
As magpie said, make sure your OH does everything for now, including bringing you food and plenty of water in bed. Eat hot food, drink lots and lots of water, and rest as much as you can.
If you can get the lying down feeding position working, that's really worthwhile: it let's you rest a bit. It can be a bit tricky while the baby is so small, but worth looking up on the Internet, and maybe asking your midwife for help. I found that the baby needed to be lower than I expected (ie further from my head) , and that I had to lie really on my side (ie I was lying more on my back than I should).
If it's getting really hard, then consider getting a lactation consultant to help you - they'll work with you to get your feeding going as well as possible. I paid £90 for a 90 minute session, and I'm so glad I did. I'm certain that's the only reason I was able to continue breastfeeding, and I'll always be grateful we had that.
Good luck, and congratulations!