Dog has gone crazy!!

I have a 5 year old Doberman Pinscher who I have had since he was 5 weeks old. He has always lived inside and been like my baby. I have two daughters who he loves dearly and is growing up with they are 7 and 5 years old. I am currently 26 weeks pregnant and the past month he has gone absolutely crazy. He is destroying my house! He is tearing up everything soft. He chewed all of my kids blankets and pillows, all of their stuffed animals, his bed, my dachshund's bed, and recently started going into the trash can and stringing trash threw out the house. There have been no changes except the fact that I am expecting. I made an appointment with the vet and she said he is medically fine, but this is a behavior problem because he is upset about something. Now I love this dog, very much but he is about to find himself inside of a underground fence, permanently. I can't keep buying covers and toys for a dog to shred! Has anyone else had any issues with their fur baby's during pregnancy? Does it get better, or will he have resentment towards the baby?