19 month old nap

My lo recently went from napping for one hour (thats all i can get out of her) to crying hysterically when put down for a nap (never done that) taking a while to fall asleep then only sleeping for 40 min. Is this teething / regression? Or should i make nap time later? She used to do this when she was little when she needed her naps pushed back. She wakes like 6:30am and nap around 12:30/45. One day she skipped her nap but was sooo tired so I tried to put her back down at 2pm and she slept for hour. Im sure there is no answer to this lol im just pregnant and really want to rest/ nap when she does. And this 40 min nonsense is not cutting it. O and when she does wake up from her 40 min nap she is a crying crank