Arggh. We went through that for months with DD1. She's now almost 2 & sleeps as well as or better than other kids her age - so that's proof that it can all change, even for the worst sleepers. But, it does take time. She was a bad sleeper from birth until she was about 1.
Unfortunately, all you can really do is get help when you can so you can rest, try to be consistent with bub's settling so eventually they learn that a certain routine means it's time for sleep (this takes time, patience & perseverance which you just might not have for now) and just try to ride it out. It WILL get better. It's just a matter of you staying sane until it does! Hopefully it's not too long for you.