Implantation bleeding, early miscarriage or just AF?

Help ladies... I'm so confused... Has my body just gone 'tipsy-turvy' on me with a messed up cycle? Am I pregnant? Early miscarriage? Here's the story so far.. Wondering if anybody has experience of implantation bleeding - unless my cycle has completely screwed up this month (never happened before!) I fear I may have had an early miscarriage or maybe still pregnant with bleeding if this can happen?... I had light spotting last week starting Thursday (9 days ago and almost a week before my period was due) which has been sort of brown with some slight red when wiping. On the 7th day of spotting up to present I've had mild/bad cramping, back ache, some nausea and sensitivity to smells. I've also developed a cold and feel run down. I'm now 5-6 days late on my period however last night the spotting got heavier and I saw some darker 'fresh blood' and have put a tampon in to monitor. (Period coming? MC? Sorry for too much info ). I have taken clearblue digital this morning which was negative and had a preg test at docs last week - also negative. Partner and I have been TTC and have had sex throughout the month including the day before I started spotting (last weds - 10 days ago). Any advice/ experience stories would be so welcome and gratefully received ! Sorry for rambling.. Lots of info to get through. Thanks in advance. Bec x