There is absolutely no worse thing than the waiting. Knowing one way or the other is one thing - you can deal. You can start to make plans. You can move on. Sitting in limbo is horrible.
With our 2nd pregnancy, we went in at 6 weeks and saw an empty sac. Had to wait 8 long days to go back. There is that 30 seconds when the wand is in, while they are looking for the sac, that is just unbareable. DH watches my face only - to see my reaction.
Well, it was good news that time. We saw a bean with a heart beat. We saw it once more alive at 9 weeks.
I just don't think you will ever feel 100% assured until the little one is in your arms. With your experience, there is no way to help it. The way I look at it - I have had 2 pregnancies in the past. One ended in my sweet baby boy and the other ended in heart break. For me, no matter how far long I will be, this bean has just a 50/50 chance.
I highly recommend purchasing a doppler. I bought mine on ebay for around $100US. You can probably sell it when you are done making babies. When I am feeling particularly anxious, I find the heart beat and can go on another couple of days. Best $100 ever spent! I found this little one at just 8+3! It was easy to find the first time but a bit harder a couple of days ago.
With baby #2, my first sign that something was up was when I couldn't find the heart beat at 13 weeks....