Erectile Dysfunction. Can this be cured?

Its almost a week since I feel something is wrong with my penis. I used to masturbate daily, but since one week , I have noticed that my penis has gone limp, and I am getting very weak erections /  trouble having an erection. Also when in the morning when I go to poop, my penis shrinks and so does my testicles and they become completely flat. I am able to urinate without pain or discomfort. Sometimes I feel I also have dry mouth, even if I am drinking 2-3 litres of water. I have quit smoking cigarettes since the last 10-12 days, I used to smoke 4-6 cigarettes a day from the last 5-6 months. When I tried to masturbate yesterday, I got a very weak erection, and suffered premature ejaculation, without getting a full erection. My penis has become flacid, I have no sexual partner. Please help me. I am very worried about my potency and stressed about this undesirable situation. Can this be cured?