Hi Belindarose,
Congrats on your BFP x
I too had an early miscarriage in March this year,which was a massive shock as it was my 4th pregnancy having never had any problems before.
I am now 16 weeks pregnant with DC4 and am still very anxious, I think it lessens as you get further on but you replace early anxieties with others! Its only natural as having suffered a loss you are very aware of how things ended last time.
When I got this BFP I couldnt stop crying, and up until the 12 week mark was waiting for something to go wrong. As someone else suggested you could push for an early scan, my LA doesn't offer reassurance scan so my GP referred me as I was having some right hand side pain at the 8 week mark.
It was nice to see everything was as it should but the niggling doubts still remained and even after my 12 dating scan (which brought me a week further on than expected!) I still cant enjoy it as much as I have in the past.
What I will say though is that I have more understanding and realise that things were obviously not as they should have been for that particular pregnancy, I used to avoid MC or problem threads through fear of somehow 'jinxing' my pregnancy. 
Which I now realise is ridiculous as we really have no control and I take some comfort in my more rational moments that allows me to relax during this pregnancy that nothing I did caused my MC. It just wasn't as it should have been.
But that was that pregnancy, I guess what I am trying to say is that as people esp midwives like telling us every pregnancy is different and so please allow yourself some moments in the next few weeks to come to terms with your loss and look forward to this pregnancy.
Dont miss out on your special journey through fear of something of which is out of our hands. Your anxiety can be equally balanced by allowing yourself to enjoy every moment of this pregnancy.
I hope things go well for you x 