I dont know what to think 😞

I was having some mild cramping when I went to the ER to get checked because i was also having brown discharge. Has I was geting my ultrasound and blood work done, the Dr comes in and tells me that I am 100% pregnant BUT they could not find a baby. He couldn't tell me anything after that because he never seen that before. I have to go back next week to see if my numbers go up to get another ultrasound done and see if there is a baby. Im scared of bad news but im just hoping its an early early pregnancy that they couldnt see the baby. This would be my 4th baby.