Sounds like nighttime post-nasal drip (the phlegm that you cough up is a big sign of that). Post-nasal drip can also cause a very irritated throat. Perhaps that it what your sensation of dryiness really is. Also, if you are having nighttime congestion you may be breathing through your mouth while sleeping, which will also dry out your mouth and throat. Combined with that congestion draining back into your throat, there are the symptoms you've described.
This might all be caused by allergies, or a sinus infection. It's unlikely this has anything to do with your surgery from so many years ago, since you've only been having this problem for a couple of weeks. And ENT, or just your regular PCP, could check out what's going on in your sinus cavities.
thanks for the help. much appreciated. the nasal drips might really be caused by my allergies. actually i was diagnosed to have allergic rhinitis since my high school years. just wondering though why it's only now am having this drips of blood and phlegm. am not worried much now. thanks!