Engine no start

The other day my car would not start. It kept turning over but would never start. Before my ex boy friend and I took anything out to test it we checked the fuse and it did end up just being the fuse. We put a different fuse in that I was not using (just temperature) and when I put it in the car started right up. Now three days later I went back to try to start the car and nothing. Doing the same thing but this time I checked the fuse. It is not busted. I put the fuse in a different spot just to be sure and it was not the fuse. I also tried to put a different fuse in and still nothing. Please help!