Possible 4th Miscarriage!

So after having 3 miscarriages and finding out I was pregnant on Wednesday, I have been bleeding on and off since last Sunday. I am convinced I am having my 4th Miscarriage. I have to wait until Wednesday to go for a scan as I will be 5 weeks. Why won't my body let me have a baby?! I knew this was to good to be. The EPU said on the phone it's was implantation bleeding but can this really be going on for almost a week on and off? I haven't really had any pain as such just some dull period type cramping. Please can someone give me their advise? Thank you in advance.