My 6mo was sleeping through the night from about 4months. We felt so lucky. Just before 6 months she got a cold which was hell and meant she woke to nurse every 2 hours. We got through it. But she's had a new habit ever since of waking at 2am, 4am and 6am to nurse. If we're lucky, she just does the 2 and 6 but we're often not. We've tried other methods of settling her and we're tried just letting her settle herself but they don't work and I end up nursing her and she falls back asleep.
Any tips on getting back on track? She gets enough during the day and is on solids. Her nap routine is great. It's just the bloody night time that's gone a bit wonky now!