I have an (almost) 8 month old girl and the above three situations sound exactly like us! She started to sleep through at about three months old, then began waking during the night again at 4 months, needing a night feed. We started introducing solids (for medical reasons, not because she was waking up) and this seemed to help for a few weeks. Then things went crazy. She begain waking around every 20 mins. Nothing settled her. She didn't want a cuddle, a feed, her dummy, a drink. This went on for 9 weeks, by which point I called my health visitor, feeling like I really couldn't do it anymore. After having her checked out by a doctor, the health visitor sent a 'sleep expert' to see me. She asked questions for about an hour (not all about sleep) then suggested I make the following changes...
1) Put her to play in her cot every day, leaving suitable toys in the cot at night.
2) Leave her door open when she was asleep. Also consider putting a CD on repeat to stay on all night very quietly. She suggested wave sounds. We decided against this. (The CD, not the door).
3) Let her sleep without her growbag (obviously we added another layer to stop her from getting cold) to make it easier for her to move around the cot.
4) Leave her be (unless she was crying about it) if she turned around, ended up face down, stuck her leg or arm out the cot. Remember she is 8 months and can easily move position if she needs to.
5) Leave her crying for 10 timed minutes before going in to see her. I decided 10 minutes was too long so did 5 mins instead with the intention of upping it over the next few days, but didn't need to in the end.
I couldn't believe it - that night she slept through, and has done ever since (it's only been two weeks, so fingers crossed!). I've sometimes had to replace her dummy once during the night, usually around 6-7 hours after she has gone to sleep. She also now seems to self settle for naps during the day a lot easier.
Obviously this advice was given based on my answers to a lot of questions, but if any of the ideas above can help anyone, go for it. Even try calling your health visitor and saying how you're feeling. I was starting to hallucinate so I knew I wasn't any help to my baby and had to get some outside help. Good luck everyone - I didn't think there would be an end to it and couldn't see a way to solve things, so I hope you find your way too.