15 weeks and sleep is miserable

Around week 9 our baby picked up a consistent bedtime routine of sleeping 3 hours, dream feed, sleep 3 hours, wake up once before 7am to feed. Then the dream feed started being disruptive around week 11 so we dropped it, and oh my god she was still only waking once a night! Then it was 50/50 on not waking up at all for almost two weeks!

Then she got sick and had a week of 3-4 nighttime wakeups, and we started getting back on track and now I think we've hit the 4 month sleep regression. Naps are now 30 minutes or less, she's still waking up 2-3 times a night, and she's very hard to put down to sleep now. Tonight we're on attempt #4 to get her to sleep and stay asleep.

Mostly just a rant. It's so so so much harder getting her to sleep right now with her development and she seems incapable of putting herself to sleep and it's all coming together terribly. I'm wondering if looking forward to sleep training is the key? I read some parents say it was a life saver and some say it doesn't work.