Possible menstrual cycle but positive test?

[S1919]

The background to my story is I had a miscarriage in March this year and it wasn't straight forward. I had septic contents and rushed in for an emergency operation (so this is where my paranoia comes in). My 2nd miscarriage happened on 10/10 at 9 weeks for me but baby measured 6weeks.. By 16/10 no signs of miscarriage happening so had medical management. Things got started within 3 hours.
I was told if still testing positive at 3 weeks to go back for blood test which I tested at 4 weeks and was positive so had my test that day. That was 18/11. My HCG levels was 31 and they said to come back in a fortnight if I test positive again by then.

So 19/11 I start having spotting for 2 days.. Then I've had light bleeding for 2 days. Very little on the pad at all. I'm thinking yes this links in with menstrual cycle but a friend as suggested a probability that it's implantation bleeding because of the colour and the flow.
So just out of curiosity I've done a test and sure enough there is still a positive line on my test.
I've google and googled and got no where as to how it's possible to have AF but still have a positive test.
My mind is all over the place.. Trying to wait until 2/12 to do a test is proving impossible. It's definitely easily said than done. And trying to not say much about all this to SO and family as to not get their hopes up.. Very overwhelming experience.