Hi,
I have exactly the same problem, except that it has been going on in our case since birth.
I, too, am at my wits' end. When our dd was 4 months, we just co-slept all night because it made things a but easier on me. She woke up, I rolled over, she helped herself to my boobs.
It was ok for a while, but not a long-term solution for us, as she still fed every hour and walso wanted to cluster feed for two hours from 2-4, so I was still exhausted.
DD is now 7.5 months.
I have always said I will never do controlled crying, so I consulted a sleep specilaist.
She said to bring the cot back into our room, whcih we did. We then put dd in it at the start of teh night and had to teach her that this was where she slept. This took a while. She cried and we would comfort hrer in the cot - stroking and patting, etc - unless she became very distressed, in which case we would pick her up, calm her and then put her back.
By the third night, she was settling well in the cot, but still waking frequently.
We were also told we needed to break her sleep association - ie breastfeeding to sleep all the time. So I would feed her downstairs before starting bedtime routine.
Bedtime routine is a sleep association, so is her cot, and so is a rabbit that she has only at sleeping times. The rabbit is the only thing she has in the cot and she sucks its ears now to get to sleep.
What I reaslised throughout this is that, despite being 7.5 months, she is still geuinely hunry every three hours. So I also feed her now every three hours.
Anyway, we did this religiously for a week, for herdaytime sleeps and every time she woke up at night. It helped in some ways - ie she went to bed at a sensible time and slept in her cot. Her day sleeps were also improved.
However, she then got ill and that messed it all up.
But she's better now and we've been putting it back into practice. Her day sleeps are rubbish again - she wakes after 40 minutes and it is long, hard and, frankly, depressing work egtting her to go back down, even though I am sure she's exhausted
She also still wakes every hour.
So tonight, very reluctantly, I am resorting to controlled crying. I really, really don't want to, but I am at the limit of my well-being now.
I hope you get yours sorted. Maybe some of the above will be useful for you. Maybe not.