In order to flop my kids around I just promoted sleep all the time any time they were willing to. So if it's all day so be it. I found that trying to move it myself wasn't helping, so allowing them to sleep well shifted it on it's own. I know it sounds counter intuitive, but it helped us. I was loosing my head on my 1st because I had to be at work at 6weeks & had no idea what to do, so I gave up...and when I did he sorted out. Go figure. So on the next kids I did that too. I just rode it out & they sorted. It's not easy. OMG it's not.
The other thing that is always useful to me that whole first year, any time I feel like the sleeping seems unpredictable, is to start writing it all down. If I write down all the sleep times as best as I can (I know that is hard when you are deathly tired) what I would find about 3-5days in, was that there was a pattern. If I looked at how long they were awake & how long they slept. It felt random, because the times on the clock were changing, but in reality it was quite predictable. So it might look something like : Bay is awake for 60-90mins, then sleeps for 20-30 mins, then is awake 45-60 mins, then sleeps for 1-2hours, then is awake for 60-90mins, etc etc. What I saw was sanity in that chart. It won't change that you are tired, but it helps you feel a little less like your entire day is entirely random.
And the best news I can give you is that it passes. It does. They do sleep, at night, and so do you. Hugs to you both. Sleep deprivation is the devil.