Just as you think you've got yourself and your pup into a tolerably workable routine, teething comes along, accompanied by the growth spurt, and possibly just a little of the huge excitement that comes with having a new pup wearing off a bit. Added to this you have renewed sleep disturbance.
I found this stage tough even though I had retired, so be kind to yourselves going through it, because like it or not, it is a Thing that must be Done!
You're doing really well, just hang on in there a bit longer, keep repeating the mantra, and before too long things will start to settle down again, this time with no more major disruptions (eg teething) in store. That's when the really lovely times start and carry on......