What's going on with me?

Brandi • 24, married and pregnant with my 2nd which is also my rainbow:)
My period is pretty late. Almost 40 days since my last period. I've taken 3 pregnancy tests and went to the doctors and all said negative. My period has never done this. Its driving me nuts because u can't continue to ttc until my period comes and goes! Any ideas what's could be wrong?