Lighting, Light Fixtures, Ceiling and Exhaust Fans - help with light

A while ago i asked for assistance with a ceiling fan in one of my bedrooms. Tee light stopped working, so i switched the entire ceiling fan/light with another one that i had. After switching it I was under the impression that the one that i took off was faulty since the new light and fan worked. However the other day i turned on the light only to learn that the problem of the light not working has reoccured.
When i turn the light switch on the light does not go on. Two days later the light went on( I guess i left the switch on). When i had the first problem i checked the switch and the wires all seemed to be tight. when i installed the current light/fan i made sure that all of the wires were tight and in place.
Any ideas as to what can be cauing the light to not work all the time?
We will be using this bedroom ni a few weeks when my wife gives birth, so i need to get it fixed.
Thanks,

Intermittent problems are usually caused by poor connections. In addition to causing intermittent operation, poor connections usually cause heat, which is an even more serious problem. Check all connections. Be especially suspicious of wires poked into holes ("backstabs").

Also, sometimes switches fail and need to be replaced.

If the fan has a remote control, it could be part of the problem too.

There is no remote control, I will attempt to replace the switch sicne i have an extra one, Well see if that is the cause.