My collie had pups 8 weeks ago tomorrow. We are hoping to get her spayed once all the pups are rehomed in the next few days.

However, the past few days I have noticed spots of blood where she has been sitting and can't find any cuts or anything on her, so is it possible she is in heat again so soon?

Suggest yoe give your vet a quick ring. The nurses should know a definitive answer. A quick look on Google suggests it's unlikely and it may be indicative of some sort of problem.

Thanks, I will have to do that