history: I miss my old dog. I was thinking about getting another one but it won't be the same. I miss my old dog_comma_ I was thinking about getting another one but I'm not sure. How long has it been since you had your old dog?
current: It's been 2 years, so I'm out of the habit of walking, cleaning, etc.
next: It might take a bit of time to get back into the swing of owning a dog. I'm sure you'll be ready soon if you still think it over.