Advice please

Rebecca
Is it possible that pregnancy won't come up on a blood test? Currently 54 days late multiple hpt BFNs and 4 negative blood tests. Thyroid problems but on medication that doesn't affect my fertility or my periods. 
​Current symptoms
​Frequent headaches
​Some nausea
​Big appetite 
​Hot and cold flushes
​Sore back 
​heavy and sore breasts
​Any advice would be grateful