My last period was August 28. I am having some cramping and nausea but no period. I have taken two pregnancy test both were negative. Could I still be pregnant

Very easily.

First how many day cycle do you normally have ?

Are you often late ?

How late are you ?

Unless you are at least 14 days late, you really just need to wait before you test.
And even then a false NEG is possible.

Also when are you testing, it should always be first thing in the morning as soon as you wake up.