Thanks jick for the reply. I do not see any signs of water in the motor oil. Its still oily to touch and black as it hasnt been oil changed for about 3 months. Radiator water is also clear with no indication of oil.

We will try to have a compression test. But getting back on my question, whether it fails a compression test or not with the symptoms on hand (small bubbles in radiator and gas fumes in water) can this be done only by replacement of headgasket?