clare van santen , 37 , has stage 4 breast cancer , which means it 's terminal .
single mum-of-five was first diagnosed in 2005 while pregnant with her son .
she underwent chemotherapy and a mastectomy to fight the cancer .
then in october 2013 she learned it had spread to her liver and shoulder .
discovered she had tumors in her brain after a seizure in february 2015 .
now she has thrown her support behind the buying time campaign .
it urges people to donate to fund more breast care nurses and services .