Tb skin test negative, quentform TB test negative, bone marrow biopsy results indicative of TB (reacts to ziehl niehlssen), PCR negative. How come?

No...actually. The zn stain is a broad stain for acid fast bacilli of which mycobacterium tuberculosis is one of many. The specific tests like quantiferon or the pcr test are against you having tb. The culture is the "gold standard" but you will need to wait for it. It might turn out be a cousin of TB and that too will grow out of culture. Stay on TB meds until they are certain of the AFB positive organism.