When ever I pt my fan on I'm sure it's putting the exhaust fumes into my car it stinks of diesel when ever I turn the heater on and make me feel sick after a while dose any one know what the problem or solution could be(except not using the fan)

I'd say that you have an oil or diesel leak which is being burnt on the engine.
It seems that the GP will readily pull air from the engine bay when the car is not in motion.
All i could suggest would be to investigate the source of the smell.

There should be a rubber seal along scuttle, to seal the rear of the bonnet, to prevent air from the engine bay entering the heater. Might be worth checking this for position and condition, although they are not meant to be a perfect seal, just to discourage the fumes to get through.

As Keat63 says, lift bonnet and look/sniff for the cause.

Take a look at the breather hose i can guaruntee its that if so its a £10 fix buy a pipe off ebay