rex won't start... please help

so here's the deal. my car started doing this a few months back. i would try starting it and it would just crank but not turn. it only does it from time to time, and after a few tries, it starts. i did however pay attention to any patterns for future reference. so, i noticed that when it didn't want to turn over, the faint buzzing noise when just at the accessories position, was not heard. then after a couple tries, i'd hear the buzzing from the gas tank area, and it would start. this pattern has been constant. then the other day i was off to work as usual, and it did it. no buzzing at acc. position and no start. i tried and tried and tried and tried, and then tried some more. nothing. the funny thing is, when i got home that night(i work from 2:30pm to 11 pm BTW) i tried it for ****s and giggles, and it turned on. so the next morning, i figured i'd try it a little earlier to see if i could take it to work, and nothing. no start. so off to work i went in my wife's accord. i get back THAT night and again it did start. 3rd day, again NO START. i wait til about an hour ago(night), and it does start. now i am thinking that the heat may have something to do with it but i have no idea. i am thinking it's the gas pump thou, which would suck cause i do not have $150 to spare right now but i NEED my car now. but my best friend told me that it may be the main relay. the buzzing noise is a for sure thing thou. if i hear it, the car starts. if i don't the car does not start. never fails. please advise. thanx in advance for any posts.