Diamonds - I was spotting a little at about 6 weeks. I called the MW, he sent me to the EPU. They did blood tests and a scan, there wasn't anything visible on the scan and the HCG levels weren't increasing as expected.
Then they did more blood tests, and even more blood tests (about every 72 hours for 2 weeks). The consultant also did an internal scan but couldn't see anything obvious.
Eventually the HCG levels led them to decide that whatever was happening the pregnancy wasn't viable. They did a laproscopy, and found an ectopic pregnancy in my right tube, which was removed. I had six weeks off work (thanks to a wonderful, caring nurse telling the young doctor what he needed to put on the certificate signing me off work), mostly the mental recovery as the physical side only took a couple of weeks to recover from.
BTW, the internal scan was fine. They use the regular 'TV' screen for viewing the pictures, but instead of the paddle-thing that they rub on your tummy they use a slim tube (covered in a condom and with loads of lubricant) which they place in your vagina and move slightly to look at your uterus and tubes from a much closer/clearer viewpoint. It doesn't hurt, perhaps very slight uncomfy, you will be decently covered and the knowing is better than the not knowing IMO.
I hope this info hasn't worried you unduly. Some ectopics are the kind of blue light emergencies you hear about, but others progress painlessly and need careful monitoring.
Good luck with your investigations Diamonds, I will be thinking of you.