Toddler tantrums!

Does anybody else have trouble staying calm with their toddlers some days? My son (will be 3 in a few weeks) has been a complete trouble maker/ disobedient the last few weeks and I'm 15w pregnant. Some days I just want to rip my hair out! I'm normally a very calm person, patience of a saint but now that I'm pregnant I want to blow my top with him quite a bit! Anybody else facing this? I thought it was the terrible twos but it's starting to look like it's going to be terrible threes instead! I think he may be picking up on the idea that I'm having another baby because he makes comments about wanting a baby and has started taking care of baby dolls and such. Maybe he knows something is changing and is acting out because of it??