How can i tell if I'm pregnant after taking 3 home pregnancy tests?

My period isn't normal to begin with. I have never missed more than a month w/o being pregnant. and home pregnancy test have always been effective in determing my pregnancy. Except this time I'm 10 weeks late, I've had spotting last month that went from brownish looking to very light pink and slight cramps but no period. This month i had cramps but still no period. I've taken three pregnancy test and they all came out negative. I'm on the brink of madness I don't know if i should wait/how long before i go see the DR. please help!!!