I am on the pill and just over 2 weeks ago I carried on another pack of pills instead of having my 7 day break. The last week I have been suffering from headaches, dizziness, feeling sick, high temperature every day and yeasterday my breasts began to feel tender

A high fever is the sign of an infection, not pregnancy. The breast tenderness could be due to the length of time you have been taking the pills, or the fact that your period should be on soon.

Just feeling hot all the time when I'm usually always cold

Then you don't have a fever?

This could all have to do with the length of time you have been taking the pill. Unfortunately, you are going to have to wait to see if your period comes.

Its not the first time that I've continued on to another packet, but I've never felt like this before

Is it possible you could have a flu? Again, you are now going to have to wait for your period to come to see if you are pregnant.