Hi I Have A Question, I Had Intercourse With My

hi I have a question, I had intercourse with my boyfriend around ovulation, we r trying to concieve, but this is only first month of trying.

my period was due at november 26, and it has never been late before, my cycle is 28 days long, and my period is always at time.

well a few days later as my period didnt show up I took a pregnancy test, which was negativ, I was like okay maybe the hCG homone isnt high enorgh for the HPT to be positive, so I waited around 5 days and took a new test, but again it turned out to be negativ, I just really have a feeling of being pregnant, and my period still havent showed up, I continued taking HPT tests, and all showed up negativ, until december 7th I got like a pinkish spot.
and on the December 8th there came like a heavyer flow, I went to the bathroom, I sat on the toilet, and I could see it raning out very thin, but red, it was like I was peeing but I wasnt, the blood came from the inside, so my question is, could I have been pregnant, and had a miscarriage?
even though all my HPT test turned out negativ, I have read that some women just cant have a positive home prgenancy test, as the hCG homone isnt high enorgh in their pee, and will have to do a blood pregnancy with the doctor, and I was planning to do that when my next period were due.
but then this a little heavy flow came.

so one more question is it possible for the doctor to find out if I were actually pregnant, and if I had a miscarriage?

can it be a threatened miscariage, or do u think it is just my period that is late?