Toddler tantrums related to pregnancy?

I’m not sure if my almost three year old is having tantrums for normal toddler reasons, my pregnancy setting it off, or a mix of both. I’m also extremely lost at how to deal with them while I’m dealing with everything else.

I’m 16 weeks along with our second and I’m just starting to show fairly well. Our daughter has known about brother for weeks now but I don’t think she gets it fully quite yet. She has always been very vocal about her feelings but has never really had tantrums. About 1 1/2 - 2 weeks ago she started having massive tantrums at school and home. My mom, who works at her preschool, has mentioned how explosive her behavior has become. I’m really at a loss because she’s always been fairly calm with one or two issues here and there. Right now, we are averaging 3-6 tantrums an hour. Anything and everything sets her off (being told to wait, eat dinner before candy, me also eating dinner, etc).

Are there any second time moms that can give any advice?