Cap'n,
went through exact same feelings and emotional distress as you are when I had to take my Brittany Spaniel to the vet to have her put down one week before week Christmas.
That has hurt me inside still to this day. I still look for her and am reminded she is not here any longer.
It gets better but it takes time. I know exactly what you are feeling. And, it's perfectly normal and fine to actually LOVE your pet. Me and mine were inseparable when I was home. I am sure you were the same way as was Ribit.
Grief and missing someone you love is a hard thing.
I loved that Rainbow Bridge piece Ribit posted. I shared it with a lot of people today.
I hope your grief will go away quickly. It's real and yes, it hurts, even grown men and even Marines.
Your dog was your best friend and you had a lot of affection for it. You miss it.
Remember that there is no answer for pets being in heaven in the scriptures. Best we can say is that GOD always tries to make us happy.
Best,
micro..