Oh mamas, I'm with you. DS is just over 3 and suddenly needs me ALL the time, daddy won't do anymore, he's constantly breaking down into tears/whining sessions, won't do things by himself, etc. Yesterday he FLIPPED out because I went out the house for 2 hrs; something that would never normally phase him. I haven't been sure how much is to do with upcoming new baby and how much is a stage he's in.
Thinking about it more I think it's natural regression; 3 is a huge shift developmentally when they becaome much more independent and we suddenly increase our expectations of our child. They're learning a huge new amount and I think it's a case of 5 steps forward, 10 steps back, iykwim?
I'm realising now how much of a big deal we made out of DS's 3rd b.day and being a "big boy" and today is his first day alone at nursery school...all things he's been really excited about but at the same time he is walking around all day in a baby voice saying "I'm your baby boy". Must be scary to grow up and change so fast and I guess they have to cling onto still being our little babies and making sure we're still there for them (I always tell him, yes you are my little baby, AND you're a big boy sometimes too).
I DO think they will work through this phase...I know a lot of 3 yr olds who've regressed but don't know too many 5 year olds like this!