2000 Toyota Camry won't start. Recently changed the battery, timinig belt, battery cables, and starter.

My car refused to start this morning. I've already changed the battery, timing belt, battery cables, and starter in the order so at this point I don't know what it could be. I first started having trouble with it last month when it started getting cold; when I took it to my mechanic he said it had jumped timed, so my grandfather and his friend fixed it at his shop. A week or so later it started to have the same problem, but it would always start until it broke down one night when it was really cold and it was sitting outside for twelve hours. Before it broke down the last time I took it back to my mechanic and after changing the battery cables, keeping it over night and restarting it several times both the night before and the morning I came to pick it up. The morning I came to pick it up it wouldn't start the first time I tried and then after a few minutes it started up fine, so my mechanic told me that it was most likely the starter motor, it broke down the following week and wouldn't start. I changed the starter myself, and its been starting and running great for the last five days, but then this morning it wouldn't start. So I have no clue what this could be. Any ideas?