No period, but negative HPT?

[Strawberry111]

I've been hunting for answers, all over the WWW, and mumsnet seems to be the most friendly and helpful so I thought I'd put my worries out and see if I can de-stress.

I am 20, I'm currently going through a few hospital investigations, I was turned away at my CT scan as they feared I may be pregnant.
At the time I didn't think allot of it until I worked out I was actually late. So they rebooked me in for the 27th (tomorrow)..

During the week I've bought a few tests, a regular one from ASDA, both negative. Still no sign of my period, I bought the cheap ones in poundland.. Again all negative! But now I've developed more symptoms, sickness, swollen breasts currently no pain, and lower abdominal cramps that come and go? I believe I was due between the 17-20th this month, I am irregular, but my previous periods all start between those dates.

This is my fear, I am due to have my CT Scan tomorrow, but I feel I am pregnant? I've waited months for this scan, the one thing that's stopping me from postponing it is that my tests are negative, I wouldn't want to risk having a scan due to the radiation.. But since my tests are negative, this is my dilemma!!

It may be worth adding that this is my 2nd pregnancy, I discovered at 6 weeks with all the symptoms, which ended at 8 weeks I suffered a miscarriage, I'll also say I had the mirena coil removed 7 months ago after having it for 7 months. I'd also only be around 2-3 weeks if I am pregnant, could my HCG levels be to low for detection?

I may be thinking in to this to much but I'm nervous, and my general health isn't brilliant so I'd want to tell my consultant as soon as possible if I am pregnant.

Sorry I must sound silly going on! Thank you in advances ladies. Have a good day!

I was pregnant and my first preg test that I did was negative, simply because it was too early to show I think (i would have only been 2 weeks). I tried again one week later and they came up positive. Sorry I don't have any specialist advice but I just wanted to let you know that! I used tests from Bodycare that were a £1 for 3 and they worked :)

If you are 6-9 days late as your dates suggest then any hpt should pick it up. Is there another reason it could be late? Stress of illness? If you're really sure perhaps go to the doctors and see if they'll do a blood test. I can't advise about the ct, can you Google and find out the risks, they may be minimal.

I bought the 3 for £1 dip stick also lol! Thanks for your response ScarletStar, I've read that some women haven't had a positive line until they where well into their pregnancy, I found out at 6 weeks as I had no idea I was pregnant. So I couldn't comment on the first few weeks of the pregnancy.
And Sanch, although I have some health issues they have never affected my periods, nor have I been this late before. Except the time I was actually pregnant.
I'm going to pick up a Clear Blue test this evening, from my understanding they are more sensitive than others.

Thanks for the responses guys!

ClearBlue told me I was pregnant about a week before the regular HPTs did. So I do think they are more sensitive. Good luck!