1996 Pontiac Sunfire help, whats wrong?

I drove my car to the local Home depot and when I came out to leave it would not start. Sounds to me that it is not getting any fuel. My gas gauge has started to look as if there is fuel in it but I have ran out a couple of times. I know that you are not supposed to let it run out completely but as I say the gauge is not reading right. So back to the story. I had someone take me to get more gas and it did not start( sounded like it trying to turn over but just didn't have it. I called a tow truck. He took to my home and I left it sit for about 4 hours, I came home and started. I filled it up again and also changed the air filter ran good for a few days.I went to a DRs appt and had about a 26 mile drive, took care of my appt and came out to leave and it did not start again. I had someone take off fuel filter and put it back on still didn't start. My ex husband said to change the fuel relay with the air conditioner and it then started again. I went and bought a new relay and put one back for AC. Drove the 26 miles back went into eat and came out and low and behold it did it again. Help please, I don't have the money to take in and have it torn apart and then not have the money to put back together again. Does anyone have any suggestions please? To me it acts like the way older model cars used to vapor lock. Is there something like that in newer cars?