I can't love him yet

My boy died on March 12 after years of battling cancer, he was just not strong enough to fight anymore and was taken from me at 14 years old. He was my everything and he was the reason I lived and wanted to stay alive just for him. I do have another dog (11year old German shepherd girl) and since his death she was VERY depressed and didn't want to eat or move.

after about 3 months I was recommended by my doctor to get another dog to help with my mental state and also the vet recommended that I get another one for my girl. I did and made sure to get a rescue.

He was 7 months when we got him and he's 9 months now and so sweet, loving, cuddly and loves to play and learn to do commands. But I just don't love him, he's not my Jack, he isn't my baby boy and they're so different. I feel so bad saying that if it meant I could get Jack back I'd give up Tobey (the puppy). I hate it that I feel this way and I feel so guilty. I know it takes time and I must just heal from the loss. I just want my baby back.