Toddler refuses to sleep or nap?

My daughter is 23 months and the past 2 weeks she has refused to nap or go to sleep at her regular time. She used to nap from 12:30-1:30/2 and go down for the night at 7:30 pm and sleep until 7:30 am, and now I will put her in her room to nap and she just stays awake, I usually only leave her an hour (she just plays quietly, doesn't cry) I have tried putting her down later for her naps and that doesn't help either, but she is just so miserable in the afternoon, by 3-4 pm she is extremely grumpy, but won't even sleep then, it makes it hard to get out and do anything as she just cries and is very fussy, I will put her down at 7:30 pm and she stays awake until 10 pm!!! I am 8 months pregnant currently and exhausted, I am not sure why the sudden change in her routine? I haven't changed anything and she isn't sick. The mornings are fine, she is completely happy, I find the afternoons tough as she I can't take her anywhere since she is constantly throwing fits over the smallest things (which she usually isn't like unless she is tired) Anyone have any tips? I am feeling so exhausted dealing with this and am unsure what to do, is it just a phase? I just find I don't get a moment to breathe anymore (when she is in her room for the hour, I shower, clean what I can) Any tips or advice are appreciated! Thanks