Ok, I went to mechanic and when he drove the car, he said the bearings are 100% fine, the humming sound is due to the hardness of tyres, and he recommended that you replace the tyres, so I replaced all four tyres with new ones and bought Nexen 185/65/R15 (Previously my car had 195/65/R15 Yokohama). People here recommend Yokohama, but the Yokohama Tyres are hard and hard tyres give noise/humming sound. So I compared both Yokohama and Nexen, and found that Nexen is much softer than Yokohama. Also, I checked the cheap ones too (Eurostar), they are more hard like a rock. So after checking and comparing all the tyres and their prices, I installed Nexen, and believe me, the car is now smooth and the noise is totally gone. Even at 120+ there is no humming sound.