Ford Fiesta fog light button stays on and engine cuts off when lights are turned on! help!!!!

Hi everyone hoping someone can help me I have a R plate fiesta. Recently the fog light button in the car stays on and won't let me turn it off no matter how many times I press it. It happened the other night and whilst the fog light was on I turned the headlights on and the engine cut off. When I turned the lights off the engine started fine and when I turned them on again the engine cut off, the same happened when I put the hazards on. And finally as I got it working the headlights came on even though I didn't turn them on when I pressed the fog light button it turned the headlights off. Also every time the fog light comes on the needle on the petrol gauge falls past the red line on the gauge. When the light goes off on its own the petrol gauge climbs. I really need help guys hope yous can help!

Thanks
Mmp