Will not start

I took my car to a mechanic and had him replace the timing belt, valve cover gasket and do a tune up. After I got it back it started to act weird. At times it would not start but it still cranked over. I would turn it over four or five times and then wait for a minute it would start. It did this intermittently for a while and you never knew when it would happen. I took it back to the mechanic to see if he could find the problem. After a day of trying he finally got it to not start. He did some testing and found out that when it would not start the checking engine light did not come on when he turned on the key. He then replaced the main relay which seemed to fix the problem for about a week and the it started to happen again. I bought another ECM from Ebay hoping that was the problem but that did not work. Right now I cannot get it to start no matter what I try. The check engine light does not come on at all now, so I have a large paper weight in the driveway that I cannot start and no way to take it to a mechanic. Help! It is driving me crazy.