Schedule/routine

How did you mommas get your baby on a routine/schedule?

My daughter will be 5 months on Monday & her schedule & routine has basically been thrown out the window..

She had a great sleep schedule & routine, up at 8am & bed at 8pm. & since she’s turned 4 months, it’s like it never existed. I was pretty sure it was the 4 month sleep regression, then today I realized she has a tooth coming in.

Right now she goes to sleep anywhere from 3am-4am & will sleep until 1pm. I try so hard to get up early & have her wake up, but I am just so tired.. I need advice. Should I get her up early? Or just continue to let her work it out until we get our schedule back?