Hi dire.botma, the symptoms that you have described do very much suggest of pregnancy
but as your preg-card test is negative,it does seem unlikely. It would be better if you got your urine HCG done once again and also an abdominal ultrasound
to rule out any extrauterine pregnency. Sometimes the embryo gets implanted in sites other than the uterus
and is not able to survive but can cause a bleed which may explain your bouts of dizziness
. Also the period like experience that you had could be because of implantation
bleeding. If the fetus is not viable then the pregnancy test may come as negative.These are possibilty and not a certain diagnosis and it would be woth your while to visit your gyneacologist and get as expert opinion. Take care and best of luck.