could I still be preggers?

Ol
Hi guys. 
I've recently had 2 miscarriages at 6 weeks ( march and again in May) 
We have stil been trying straight away after theese miscarriages but now I'm confused...
Cramping 1 week before period was due and experienced a lot of heart burn.. 
Took a pregnancy test Friday 16th and BFN and AF arrived the next day. Ovcorse once again another month wait and I was gutted. 
This AF was super heavy more than normal! 
However since AF my boobs are killing me and feel huge (I know this is normal for some but not for me) and I've been feeling really nauseause. Do you think this is all on my head/ coincidence or could I still possibly be pregnant?
I have one test left and don't want to waste it as I spend a fortune each month.  Please help! Xx