Dd is 1 and has become a terrible sleeper. She was doing really well up until about a week ago. She would have two naps or one depending on what we were doing and then she would only wake up once in the night. I was quite happy with one night time waking as this was extremely impressive for her. She now wakes 3-4 times a night and doesn't nap in the day. As soon as I put her in the cot she screams (we live in an apartment so screaming is not ideal). In desperation I have tried controlled crying, CIO, pupd, staying next to her bed and now I'm currently on a mattress in her bedroom. She never gives in, if she doesn't want to sleep she won't. I also wanted to give up bf but I started again as its the only way to get her to sleep on me in the day. I would really like some advise as to how to approach this problem of her not sleeping and screaming when she is in her cot. She thrashes around and really tantrums. I feel as though I'm awake all night feeding her and its really affecting all aspects of my life, my mood, my relationship with dh and my other dd. dd2 has really pushed us to the edge.
If it's only been a week that she's been like this then my first thought would be some temporary physical cause. Teething? Cold (it can be hard to tell at the start when it's just a sore throat) or ear infection? Have you tried calpol/nurofen and if so does it help at all?
Alternatively it could be a developmental phase... is she just learning something new eg walking, first words?
If you're sure there is no pain or illness, and no developmental stage, and it doesn't go away within another few days ... I'd say keep trying one of the methods you've been trying. (Not pupd, she's a bit old for that I reckon and you'll do your back in!) However you do need to pick one and stick with it, as they all rely on consistency to work. But tbh I reckon there probably is some underlying cause - I hope for your sake it is short lived.