Amy loads of luck for your scan today, chances are the everything will be just fine..
Corrin as others have said, every pregnancy is different and the first weeks are terrifying after a MC. I was the same with this pregnancy, but 13+3 now and all seems to be going well. I have had some early scans, first was just for reassurance and it did make me feel better. After that I had some spotting and bleeding, so an EPU and another private before our 12 week. I would definitely recommend a private scan if you can, it made me feel lots better. Was scary going and scanxiety was awful, but I did feel better afterwards!
legend I was definitely bigger sooner this time round, it's 2nd baby, 3rd pregnancy. By 8 weeks I couldn't do up my normal jeans anymore and was in maternity jeggings by 10 weeks. I feel enormous, like I look like I'm 20+ weeks already, but with DS I was in regular clothes until 20 or so weeks I think. It is definitely mostly fat, as my tummy is flabby and wobbly rather than hard like a pregnant belly. I can feel my uterus and it only gets to my belly button for now..But so much more comfortable in maternity jeans 
I'm suffering with headaches at the moment, waking most mornings with one and also waking at about 3am and taking ages to get back to sleep despite being exhausted..
Considering getting a doppler now after all the talk about it, but still worry that I'd worry myself more if I can't find heartbeat...I'm feeling quite relaxed at the moment and positive that everything is going to be fine with this pregnancy now...but the extra reassurance of hearing a heartbeat before movement starts would be nice..