Sleep regression?

My 2.4 year old seems to be going thru sleep regression maybe? Is there a way you figure out what exactly bothering her? I’ve read up on it but i can’t seem to figure out what exactly bothering her. I have always known why she wakes up at night, she’s usually a good sleeper unless something bothering her. She’s been waking up at 11pm almost every night, for a month now. She wakes up slowly crying saying mommy, to starting to cry harder till i have to go in. Someone told me it could be cause I went back to work a month ago after 4months maternity leave? But i don’t see anything about it to read up on it to see if it’s true. All teeth are in so it’s not teething. Bed time is at 8 to 7:30-8, usually we will let her wake up on her own. We are figuring out too if we need to drop the last day nap early? But her wakings are not consistent with whether she napped that day or not. Plus Everything I’ve read on it said it’s too early. Anyone has experience kids waking up at exact time of the night, cause that’s seem to be what’s bugging me that i can’t figure out. Thanks all.