Hi there venkat! Sorry you are in the position that you have to be here but if you have this disease then this is a great place for support and advice - and everyone here has given you great suggestions. Congrats on being a 3rd of the way through treatments. It does get harder but you'll get through it fine. Do see if you can get the magic mouthwash where you are. It's a combination of numbing medications. It helps during eating - I used it in combination with my pain medication for about a week and a bit at the end of my treatments to help me get through it. The mouth sores are all part of the process... The whitish stuff might be thrush - ask your doctor - if it is cut down on the sugar you are taking in (not sure if you are eating sugar or not but it can have an impact on thrush). And yes the drool will eventually be replaced by dry mouth. Most of the time I'm okay -(I'm 3 months out) but if I talk a lot im blessed with sahara mouth! But for now just do the rinses religiously!
Also exercise your jaw as much as possible! I used to manually stretch it (make sure your hands are clean) and I was told this by my naturopalth - if your mouth isn't too sore and too tight (which it probably is at the point) - put on some clean gloves - take two fingers and if you can massage the muscle at the back of your jaw where your teeth meet - that should help with the trismus - it apparently helps relax the muscles- keep stretching though - all the muscles actually - it's important during the first year post op - because radiated tissue - can lead to fibrosis - helping to return blood flow to the area through massage and exercise (neck too) can help with this. it may not completely prevent it but it can certainly minimize it. You may not feel up to doing all this now, but if you can - do.

Good luck you are doing well... Just a few more weeks to go!