Wow, what a disappointment to think you're in the clear and then be back to square one!!! First off, have you had him seen by your doctor? Sudden fussiness always concerns me a bit, especially after a long time of being 'normal'.
That said, something I've seen in lots or high need babies is the back and forth...you think you've turned a corner, only to discover weeks later that your baby is still extra sensitive, needs lots of extra work, and their sleep has gone out the window. This happened many, many times with Sammy. It was SO frustrating. We'd get into a great routine, he'd be so much easier, sleep better, and then BOOM! Teething, moving, vacations, you name it, back to square one.
I would HIGHLY encourage you to do some type of sleep training. Not necessarily CIO (although you may want to consider it), but something. I'd recommend 'Sleeping Through the Night' by Jodi Mindell, or The No Cry Sleep Solution. Sometimes something like teething will set them off, and they won't sleep as well, and then they get into this pattern of non-sleep, which makes them fussier and makes it harder for them to sleep, and on and on. It's a nasty cycle. So, I would say work on getting the sleep under control, and then see how his fussiness is...
I'm so sorry you have to be back here
