at positions 1st and 5th, the feedback/humming is nearly annoying, the 2nd, 3rd and 4th positions still have feddbacks but not as loud as the 1st and 5th. pls help how to correct the problem. thanks in advance

Can be many things either internal to the guitar or external.

Check your expectations as Strat single coil pickups are inherently noisy.
Positions 2 and 4 and humbucking/noise cancelling.
Position 3 is normally a reverse wound pickup which can sound quieter.
The more gain and volume on your amp and the higher the pickups are mounted on your guitar combined with the guitar volume are going to naturally increase noise.

If you notice if your guitar is extra noisy compared to another it requires further investigation.
Try playing on someone elses amp and cable during the day time with no lights mobile phones or other electrical interference. Try playing direct to the amp with no effects and see if it improves.

Things you can do to reduce hum:
A quality guitar cable or one that is specially shielded.
A grounded pick guard shield if your guitar doesn't have one.
Shield and ground the pickup cavity with copper foil.
Shield and ground the pickups with copper foil.
Put humbucking single coil pickups in your guitar.
Install power isolation equipment if its a noise from the amp type problem.
Or change the amp.

If you can't get around it with how you want to play you can also get a noise gate/reduction pedal that below a set level will mute any signal.