hi there, i have had the same happen to me too, i have two boys and couldnt tell over both of them that i was pregnant till i was at least 8 weeks late. I had all the syptoms like yourself and did home pregnancy tests, they were negative, and so asked my gp for a blood test and that came back negative too. The reason for this was because my hcg levels were too low to be detected, so when i was 9 weeks late i did a another urine test and it was possitive, then 2 weeks later i had a ultra sound to confirm it. All you can do is wait, i know how frustrating it is and sometimes you feel like your body is playing tricks on you, but you know your body and if you got the syptoms you probably are pregnant, just hold on in there and look after yourself xxxx
Unfortunately pregnancy symptoms are very similar to AF symptoms. Sounds like she might be due soon. Sorry to hear about your negative blood test. What DPO are you? Perhaps you tested too early.