I'm new to breading. My (health tested) bitch came into season, so I thought, so I contacted stud. Had successful mating on day 10 and then 12 with ties of 12 then 20 mins. Then 2 weeks post mating I noticed spotting on her bed. On checking her she was very swollen, bit of red (not brown) blood, just like she was in season again. Contacted vet, went in, no infection. Vet was not aware of such thing as 'split season'. I was really certain she couldn't be pregnant as this second 'season' lasted 5 more days. I did then pay for scan to check for pregnancy, would have been 29 days since second mating. Knew she wouldn't be, and she wasn't. So now I'm unsure what to do next season. He was a proven stud. She allowed him although I did have to hold her but she was a maiden. Should I do progesterone blood tests or just allow first season to pass and wait for second true season??
Any advice, or similar stories would be great, thank you

Did you breed her on her first ever season? I would wait until second season. I also recommend doing progesterone tests throughout her heat cycle to see when she ovulates. Theres a great tool online that shows the best time for the bitch to be bred.