My period is 12 days late and I am normallly regular give or take a day either side of 28 days. I have a few signs of pregnancy ie: frequency of urination, tender breasts etc but that is it.

I have done 2 pregnancy test of which they are both negative - is there a chance I am pregnant?

There is a chance that you might be but I probably all in your head go to a real doctor and take a blood test

If you are sexually active there is always a chance of pregnancy. With that said, it is important to take the HPTs using first morning urine as that is when the concentration of the pregnancy hormone hCG is in it's highest concentrations. So, if you did not take it first thing in the morning I suggest you do.

If you have, then a blood test from your doctor is in order.

You do not mention your age, this is very important as there are hormonal fluctuations throughout life.