My story sounds so much like yours! I had a easy precious poodle and when we had to put her down, I knew she couldn't be replaced but I thought well, I'll get another one. I had not had a puppy in 12 years. My nerves were shot! My house was torn up, constant whining. I thought, oh no, what have I done! I was actually thinking about rehoming. I'm glad I didn't. I think the worst thing I did was kept comparing them. I had a lot to learn and things are fine now.
Praying for you during your grieving season. May the God of all comfort comfort you. He understands where you're at. Also Psalms 119:28 may be something you'd like to pray during this time.