Implantation or miscarriage?

Liz
Only recently, for the first time in my life I felt the joy of being pregnant, something I've wanted for many many years. Unfortunately I only made it to 6 weeks and had a miscarriage. It was one of the worst feelings of my life. That was only 8 weeks ago. 
And then I started feeling those feelings again of being pregnant, and I took a test last Sunday (5 days before period was due) and saw that second line, very faint but still there. Since then the lines have been getting stronger and my excitement has been growing. A day or so later, I noticed one small smear of blood on the toilet paper, and felt confident it was just the implantation bleeding. 
However my actual period is due today, and last night I started getting these constant dull heavy pains in my pelvis, slightly worse than period pain, and accompanied by a few hours worth of both red and brown blood. 
My first thought is, shit not again. I don't want to go through this whole miscarriage thing again. But fortunately the bleeding has stopped, however the pain continues. 
I saw a GP today and got a blood test which I'll receive tomorrow, but my thoughts are, if it's a miscarriage, it's still going to show a bhcg level, so it's not going to help allay my fears until a second test shows higher levels. 
I'm hoping it's just more implantation pain and bleeding, but I'm so terrified that I'm just going to start bleeding heavily like last time. My anxiety and pain has me stuck in bed today, and I guess I just wanted to tell someone, and I'm hoping maybe you guys have some magical advice to relieve my stress.