Help please need advice!!!!!!!!!!!!

I had a blood test last week it was negative but this week my period was scheduled to come on Friday so it is four days late I also have constipation nausea vomitting and cramping on and off boobs are really sore so today I did a hpt and it was negative so I read online you period could be late due to hormonal problems but I got all that checked last week it came back normal I also seen online some people don't know they pregnant until 6weeks  or later so is that what's going on with me... Need advice