I have just returned from an ultrasound scan at the hospital. I found out that I was pregnant last weekend and have decided on a termination, hence why I went for an early scan to make sure that I was definitely pregnant and to get the ball rolling.
While I was there, the doctor who scanned me said that I was around 5 weeks pregnant, however I would have to return at 6 weeks, to confirm that it is an actual ongoing pregnancy? I am a little confused as to what this means, as on the scan there was an obvious black ball which indicated an embryo.
The doctor said she'd have to re-scan me because all she can see is the sac, but no other objects inside this sac. I don't really know what this means. She says it could be because I am just not far enough gone to detect a pregnancy (however I thought terminations could be done extremely early), I could be ready to miscarry? (which doesn't sound too promising) or it could be an ectopic pregnancy (but surely a doctor would be able to distinguish whether the embryo was in the uterus or the fallopian tube? As far as I was aware they were completely different structures!)
Any help on this would be greatly appreciated. I just don't understand why she couldn't confirm an on-going pregnancy at 5 weeks, but will definitely be able to confirm it a mere 7 days later?
Could I be preparing for a miscarriage? Or could it in fact be an ectopic pregnancy?

Why have you not made an appointment with an OB/GYN and asked for a D&C procedure? You asked for an early ultra sound, and that's what you got. It was too early to draw any conclusions.

D&C (Dilation and Curettage) Procedure: Surgery and Recovery (http://women.webmd.com/guide/d-and-c-dilation-and-curettage)

I didn't ASK for an early ultrasound. This is what was given. I had no idea what was going to happen when I went to the hospital.
When I initially found out, I went to see my GP who gave me a phone number for the gynacology clinic at my local hospital. I made an appointment for later that same day, attended the ward, was told I would have a scan, blood tests, STI testing, contraception advise and to discuss the types of terminations available. I was told I'd be there between an hour and a half- 2 hours.
When I arrived, I was told to drink lots of water and to wait in the waiting room. They then came in and told me that my scan was ready to be done... to which I was sent away straight after with inconclusive results.
The reason I posted this question was because I would like to know if this has happened to anyone before as I am worrying it might be an ectopic pregnancy. The longer they leave me, the more advanced I become in my pregnancy, I just want this termination as soon as possible, and I don't know why they have left me for another week.

Firstly, there are no doctors here who can tell you exactly what is going on. I am the only obstetrical nurse, so I will try to help you understand.

At 5 weeks it is virtually impossible to detect a heartbeat. We can only see that there is a gestational sac. It would be obvious to the ultrasongrapher, as well as the radiologist, if this were an ectopic pregnancy or a uterine pregnancy.

From what I read of your question, this was a uterine pregnancy, not an ectopic.

First time patient for this process?

She also doesn't mention if it was an abdominal ultrasound or a transvaginal ultrasound. That makes a BIG difference.

It was abdominal. But my mind is put at ease now from your answer that it would be obvious whether it is an ectopic pregnancy? That is my main concern.
Granted, I have decided on a termination, as it is just not the right time for me to have a baby, but the fact that the doctor said to me that it could possibly be an ectopic pregnancy has worried me slightly, as obviously the termination options are quite different to the usual ones, and I worry that my future fertility could be jeopardised.
If you say that it should be obvious to the doctor whether it is a uterine pregnancy or an ectopic pregnancy, then why did she say it could be a possibility, and make me worry for the next week?
Yes I am first time patient at this, first pregnancy, so I don't really know all the medical terms for these things.
I would just be happy to know that it isn't an ectopic pregnancy. My auntie has had two in the past, and now cannot have children. I would hate for this to happen to me. The doctor surely must have been able to just say that it isn't ectopic, but just too early to detect anything in the sac. Why she didn't tell me this, I don't know. She just sent me away thinking I'm going to miscarry, or that I have a baby growing dangerously in my fallopian tube. I definitely don't appreciate this service.