Bitch produces milk after heat cycle even though she has not been bred.....

Apart from her first and second heat cycle, my bitch produces milk after her heat about the time when the pups would be due. I have been to the vet to see if they could give me something to dry her up but they won't do anything for me, he said there used to be an injection but they dont do that anymore and to just get her spayed, which isn't an option at the moment.
I'm sure there are some people on here who could help me with this. Any opinions or help on the issue would be appreciated......