I had a blood test 9 days after having sex, which was around the time I was due on my period. So 8th Jan had sex and 17th got tested. The test came back negative but until now I have not had my period. I am worried, should I be?

Should not be worried, but I would suggest getting one of those home tests and try one my time to see.

I would make an appointment with your doctor or ob. It is worth to check things over.

There are other things that can contribute to not having a period. For example: Diet, Stress, Hormones. A doctor will pin point the cause, hopefully and rest your mind at ease.

Joe