4 month old doesn't know how to self-soothe and only knows the boob sleep association

4.5-month-old LO, 3/3/4, EBF, Bassinet, one arm swaddled, uses the pacifier as a teether, no cosleep, and at least one contact nap out of two. Room is dark, we live in a one bedroom, sound machine. She has a lovey but doesn't love it.

She hit the 4-month regression and has been waking up every 60-90 minutes. It's driving us up the wall. I cannot focus at work, and her mom is super tired. We are also first-time parents.

For every nap and sleep, I will either rock her to sleep or she falls asleep on the boob. She has never slept on her own. I have been watching the cam, and she wakes up not trying to self-soothe but fails in a minute and then proceeds to cry. This is when we wake up and offer her a boob to get back to sleep. I know she's not hungry but she can only sleep that way.

We don't know what to do. There are a few issues. We tried the Merlin suit and other sleep sacks, but she cannot sleep with both arms out. I feel like she doesn't know how to self-soothe, and the pacifier won't do anything. She uses it as a teether and then tosses it away.

Do you recommend sleep training with one arm out? Or should we get her to sleep with both arms out before starting sleep training? Either way, we need help!