First Doctor's Appointment - Not as positive as I thought

We had our first doctor's appointment this morning.  My doctor is a perinatologist, since I'm high risk due to past pulmonary embolisms + being over the age of 35.  While pregnant with Ava, I had two docs, one high risk doc and one regular OB.  I saw both of them and loved them both.  My regular OB delivered Ava but has since moved to the East coast to accept another job.  I am so bummed but my high risk doc is fabulous as well.  I'm keeping him as my global doc this time around so now I don't have to have double appointments. 
 
Anyway, the apointment didn't go as perfect as I had hoped.  I'm just trying to stay positive that it's still early and anything is possible.  We got to see the little tadpole swiming around which was pretty cool but, it's heart rate was a bit low at 118 bpm.  My doc said it was a little lower than he likes to see.  Said it should be around 150's by now.  BTW, I'm 6 weeks 2 days along, but measuring at 6 weeks 1 day which is still good.  The other thing is that there's also bleeding in my uterus right next to the baby.  The doctor said this could still be implantation bleeding and that he wasn't too worried about it right now.  He was more worried about the heart rate.  He then went on to tell us that he didn't suggest we tell everyone quite yet, which in my opinion, is the case for any pregnancy this early.  But it scared me that he had to have that "talk" with us.  He even gave us a percentage chance, telling us we had an 80 to 90 percent chance this pregnancy will last given my age and for what he saw today.  I think that's pretty good, but still, him telling us this was scary.  Lastly, the vaginal u/s revealed a large 4 cm cyst on my right ovary.  He wasn't too terribly worried about that either.  Said the cyst should minimize as the pregnancy progresses.  But that would definitely explain the shooting pains I had the last few months. 
 
So we left the appointment in a bit of a somber mood.  I guess I really thought everything would be just fine.  I am totally feeling pregnant (tired, food aversions, tired, tired, peeing every 5 minutes, tired) and I just had a good feeling going to this appointment.  Now I'm a nervous wreck again!  I've been through this ball of nerves thing one too many times and it's not fun.  The minute I got to work, I of course starting reading the internet about heart rates at 6 weeks. To my surprise, many women's baby's heart rates measure low at the very beginning and go on to have normal healthy pregnancies.  Many web sites were saying that the baby's heart rate doesn't usually start until the 5th to 6th week anyway.  Basically what I read is that anything from 110 to 150 is normal in the 6 week range, anything below 100 is too low and should be worrisome.  I'm trying to stay positive but it's still hard.  We go back in 3 weeks on the 17th and they'll do another u/s.  The next three weeks is going to be very difficult!  I just don't want to go through another miscarriage.  I just don't.  Fingers crossed and prayers please!  Thank you!!!