I have a 4-year-old rescue GSD who I have had for 2 years now. He is very active and loves a challenge. He is trained in advanced obedience and is very well mannered. However, I got pregnant unexpectedly and had to reduce the amount of stimulation I give him to take care of the baby. My daughter is now 1 1/2 years old, and I just found out I am pregnant again. I am afraid because no matter how much I do with him, I just can't satisfy him for some reason. I jog him in the mornings and walk with him. I take him to the park and play fetch with him, as well as numerous times during the day at home in my yard. I work on obedience exercises about every other day to keep his mind working. But he has begun barking and chasing things up and down the fence out of boredom when I am not present (dogs, people, squirrels, cars, etc.), which he never did before I had my child. When he is in the house, he has bones to chew on, but he whines a lot out of boredom and chews on himself. It is like the things I do for him aren't enough so he is starting to do nuisance behaviors instead, but what I do is all I am able to do with him at this time, and it isn't going to change anytime soon. I personally think that what I do for him is more than the average person does for their dog, and yet it still doesn't feel like enough. Any suggestions?

I am no expert, so I will leave the answers to the other more experienced members. But I just wanted compliment you on what you are already doing with your dog esp. considering the fact that you are pregnant.
I do know however what it is like to have a dog with a lot of energy and drive, mine whines and tires me out as well so
I am curious as well for the answer.

BACKPACK!!! I LOVE doggy packs! When we can only go on a short walk/run I strap the backpack on, put in a few full nalgenes and go. After one mile they start to slow down, and get into a rhythm instead of pulling to sniff here and there.

In about a month my 9 yr old 57lb will gets two nalgenes (about 5 lbs). Our fosters (over 1 yr) get more depending on their energy level. I've heard 10% of their body weight. During the winter into spring/summer I increase the weight on my guys to get them ready for backpacking so they can carry their own supplies. They don't get backpacks after mid-late July because of the heat.