You've received a ton of great advice. I'd just like to comment about my son, our first born, compared to 20+ other babies his age in our 'mommy group'.
My son has reflux (from hiatal hernia, due to premature birth), still at 15mos. He still has to eat smaller meals more frequently, barely able to drink more than 6oz, so he will still wake up (maybe 3-4x/week) for a feeding. The peed is completely against this, but too bad.
A boy in our group was nursed exclusively, and all was wonderful until he was about 9mos. Then all of a sudden he was begging to nurse more often, sometime every hour thru the night. After 6weeks of this, and several conversations with a lactation consultant, they figured out that her milk quality had changed. It always had a 'skim' quality. Better diet, nursing longer, supplements, etc - they couldn't get it to improve. With the peed's recommendation, she put him on whole milk and all was well again. I tell this story in case your quality is changing.
Some moms in the group tried supplementing with formula, as recommended by others, to try and get their babies to sleep better during the night. Some tried adding cereal to pumped milk in bottles or formula in bottles. None of these tactics worked.
I'm just trying to share examples of how every baby is different - 'pediatrics in a box' will not work. If you are fine with nursing 2x/night, then absolutely do it (until it no longer works for you).
Good luck!!!!