This will get complicated... Please bear with me...

I've been on the pill for about 6 months. Two weeks ago (The friday) I took the last pill, and went on my period week. However I was on holiday and had forgotten to take my new pack of pills to start the following week!
.. I had sex on the Sunday (One day after I should have started the new pack)
.. Is there more chance I'm pregnant? Should I see doc or get test? Or was the last pack still quite effective as it was only one day late?

I'm 21

Missing any pill even one, makes the effect less.. And of course as you know the pills are not 100 percent effective even when taken exactly as required.

So could you be, yes, it is far to early to tell yet, you will need to wait a few weeks anyway.