Hi I know exactly what your going through. I have 5 and expecting number 6. My kids are 17,16,14,13,and 4. The 16 and 13 year old are my stepsons but they live with us permanetly so their mine. I went through this with my oldest when I was pregnant with the now 14 year old and now with my 4 year old. It is very normal I know that. My oldest was totally potty trained and starting having accidents again including number two's when my other daughter was born. She was almost 3 at the time and had been potty trained by 11/2. When we spoke with are pediatrician she said dont put her back in diapers and dont give her extra attention for it. Just clean her and go on and dont make a big deal about it. It lasted for about 2 weeks and then it stopped. My four year old right now even though very excited about a new baby is very clingy., whiny, and wants all of moms attention. I'm just trying the same approach and not over reacting.  For instance every time I sit down he wants to sit in my lap. So I just say I cant have you sitting in my lap right now why don't you sit next to me. At first he would start crying but I just sat him next to me and kind of ignored it and now it's not an issue. I also am making a huge deal out of how much I'm going to need him to help me with the baby because he's such a big boy. He has a whole plan of feeding, dressing etc. He goes to preschool two days a week and will be starting kindergarden in the fall. Lately he does'nt want to go to school and just stay home with me, but I just say oh no all your friends would miss you at school and take him and when he gets their he's fine. I think just not overreacting is a huge trick with this one,and just not doing anything different than you normally would. I hope this helps a little. I don't know if it's the right answer but it seems to have worked for us.