No sleep at night 😴

My daughter is 6.5 months, and over the last month, she’s stopped sleeping at night. We went from a 6-8 hour stretch followed by a 2-4 hour stretch, to waking up constantly overnight. At the beginning of the night, We put her down awake and she falls asleep on her own. She’ll usually sleep 3.5-4 hours and wake up fussy. After trying to soothe her, I nurse her and from then on, she’s up every half hour to hour. I’ve tried letting her cry- she will literally cry for 1 hour plus and just seems to get more and more wound up. I’ve tried rocking her to sleep but she often wakes up as soon as her back hits the crib. I change her diaper, have changed her pajamas, added a swaddle, taken away the swaddle- nothing is working!

From what I can read online, this might be a typical issue as she’s getting more mobile and learning a lot during the day, as well as eating solids and becoming more distracted while nursing during the day. But how long does it last? We’re one month into it (I’ve been keeping track which is even more depressing). I’m so exhausted. I feel like a total failure and am not sure what to do next. I’m debating quitting breastfeeding because maybe she’d sleep better if I could control her intake? I admit I stink at letting her cry. I just can’t stomach it. But I don’t want another night like this where I barely sleep.

Help?!? Any suggestions?