if GOD exists in human body then if body becomes ill then can it be construed that GOD also became ill to that extent of disease.?

It is the Holy Spirit who dwells within those whom God has adopted into His heavenly family.

God the Father remains in Heaven, where the Son of God also dwells (until He returns.)

No, the Holy Spirit does not become ill when the person He indwells becomes ill, for illness is what afflicts carbon-based, physical bodies. The Holy Spirit is spirit.

When the Son of God added human nature to His divine nature (via His earthly mother, Mary) He did not become ill because He was without sin. He had a perfect human body for His time on Earth.

We have a huge number of real parasites that live within our bodies, there is no need to worry about the imaginary ones. If you have a tape worm and you catch a cold, your tape worm does not get the cold.

You imply God lives inside the colon as well.

When you get cancer, god just leaves you to die without getting sick himself.