So lost and confused (Lupron shot and missed period)

My last period started on August 28th a little after I got my IUD removed. My three month Lupron shot wore off September 1st. My period ended September 4th. 
Since I've had no period, negative tests, and I had an ultra sound done three days ago and was told my uterus looks good and there's no sign of ovulation for at least 7 days. 
Is there a chance I could be very early pregnant and have conceived days before ultrasound leaving no evidence of pregnancy on scan? And no positive HPTs get? 
I honestly have no clue what's going on but my period is EXTREMELY late and I have had cramping here and there but I spotting at all! Could I be pregnant!!?