6 month old waking 2-3 times a night

Hi everyone. We have been having trouble with sleep since her 4 month regression. Ive been 2 months without proper sleep and its caused me to become depressed and isolated. I dont feel like talking to friends or family. Sometimes I get irritated at my husband too. Once the doctor gave us the ok to sleep train, she slept 10-12 hrs the first 3 nights. We mastered bedtime sleep. But now she wakes about 2-3 times a night. And on 1/3 wakings it takes about 2 hrs to put her back to sleep. Ive tried everything. Modified ferber, pick up/put down. I nurse her until drowsy but she just seems to cry immediately when placed in the crib. I need professional help.