Feeling a little sad

I was at the obgyn today. If my calculations are right I am 4+1(5). I got a positive test 3 days ago.

The doctor didn't see anything at the vaginal ultrasound and said that the probability for me being pregnant is very low.

I am feeling so sad and very discouraged. Could he be right? I know that you probably can't see anything this early but he was veru negative about the pregnancy. I've had 2 miscarriages before this and I don't think I can take another... Waiting for results of my blood test.

UPDATE: I got a call from my doctor an he said my HCG levels were 100 IE/L

I hope that's enough...