No period but bfn

Hi guys I was wondering if you could help me? In currently ttc my second and last baby... And my period was due 20/3 and it still hasn't arrived I've been to the Drs and they are sending me for bloods to check everything out due to this not being the first time... And I've taken like 5 home testing kits and they all say bfn and I was wondering should I take another home testing kit or wait and see what my bloods come back and say?