Hi there Stefka, I sympathise. This is what 'worked' for me... Sorry this is a long one
DD1 was a nightmare, she only slept during the day on me and at night once asleep was fine and would sleep through from about 6 months, but getting her there was a different matter. Did CC. And though it never really worked - didn't know of MN and couldn't think of anything else. The first couple of nights was an hour and a half of full blown screaming then after that she would cry from 2mins to 20mins with us going in every 3mins saying "time for sleeping - night night." She is brill now, stories and turn out the light with some music on and she is off to sleep since about 2.6 she's now 3.8
Anyway DD2 - Different entirely - and this is WEIRD i know... i discovered it purely by chance that one day out of desperation - I was going out, just come out of shower with wet hair - As i dried it with babe in crib crying - she fell asleep - white noise i guess. Day naps were sorted - put hairdryer on floor, flick on and within 30 secs she'd be asleep and after 5 i'd go in and turn it off. My brother recorded my hairdryer for 6mins and i had a cd of 6 tracks of my hairdryer... bizarre but it worked for quite a while... I've heard the hoover works and so can the washing machine.
Nighttime, I bf to sleep like DD1 knowing i was setting up trouble for later... didn't care as it meant sleep, and i am quite selfish I guess. Have never been able to sit with her for hours in the middle of the night. Most nights she goes down (15months now) nae bother. Occasionally she is unsettled and cries. Temper mostly - how dare you leave me here!!! I didn't do the CC thing till 6 months and wasn't as strict about it as with DD1. We have been more chilled... Still what am i trying to say? Oh yes - We tried a mixture of sitting cuddling which works till i put her down. Standing in the doorway till she is asleep though when i try to leave she can wake and start the whole thing off from the beginning. I've tried reading her to sleep, she can hear me and see me, but doesn't have the cuddle and so doesn't miss me quite so much when i go. They have all worked once or twice and then she twiggs - if she cries mummy stays longer... So if i want any sleep at all i still end up leaving her to cry and i am too by this point. I know it is soul destroying listening to your baby cry like her heart is going to break in two.(mine certainly is!). However for me if i leave DD2 to cry, checking her a couple of times it is over fairly quickly - and in her waking times she is so happy and burbly she's fab so i really don't think it affects her. But you HAVE to be strong and ready to go for it - There is no point letting the lo cry for an hour and then go pick them up. YOU and DP have to be ready to leave them till they fall asleep. Guaranteed it would probably been only another 5 mins if you had held out... and every subsequent time it is less and less.
DD2 now goes down awake day or night without fuss - the odd night but that is usually teeth. Hold out hope It will get better 2 months or 20 months - you will get there. And then you forget it all anyway...