Ugh, it does sound a bit like teething. (((Hugs)))
In general, it seems like one nap starts getting cut when you get to around 3.5-4hr A. If you want a 12hr day/night, then definitely cap the pm nap. Otherwise, the day can move out to 13hr, with an 11hr night until you start cutting back and moving toward one nap.
Have you ever peeked in at the Birth Clubs? Sometimes joining in can be helpful to know what other LOs of a similar age are doing...
Birth Clubs 0-18mths Just a thought... you are, of course, always welcome to keep posting here.