A ghost story

It was midnight and I was alone at home. My parents had gone to a wedding and I thought they would be home by ten. But a storm had uprooted a tree on the main road and they were stuck at the wedding venue.
I was not scared to be alone in the house and was rather tired from a long day of classes and tuitions. Therefore, it took me minutes to fall asleep. All of a sudden, I woke up and discovered myself in an open field filled with green grass. 
The sky was cloudy and mists were dancing around the field. I could feel the gloominess of the atmosphere which was colder than usual. And then, I saw a woman dressed in a white gown and I moved towards her to ask where exactly I was. But as soon as I approached her, she disappeared. I realized that I was probably dreaming so once again I closed my eyes so that I could wake up from the dream. 
I opened my eyes only to find myself in the middle of a burial ground and I was feeling cold again. The sky was filled with dark clouds and there was a rough wind blowing. 
I looked down to see an open coffin on the ground. I was curious so I opened the lid and found my dear old grandmother lying inside. I was shocked because I knew that my grandmother was not dead. I moved away from the coffin and started to cry out loud. 
I again moved towards the coffin and saw that there was nothing. I thought that I was perhaps dead and I will not be waking up again. As soon as I thought it, I found myself inside the coffin! I do not know how I got myself in the wooden box and I shivered at the very thought of being stuck inside it, without being able to breathe. 
Then I found myself in a dark room and I began to think that I was still dreaming. However, I actually saw myself back in my bedroom and I breathed a sigh of relief.
I got up from my bed and turned on the light. I began to feel more at ease, so I went to the dining room to have a glass of water. I could feel the eerie silence that had engulfed the house. The only sound was that of the rain droplets hitting the windowpanes.  
Some moments later however, I felt something unusual. I was no longer feeling the cold floor under my feet, rather I was floating in the air and flying towards the celling. I thought I was stuck in a cycle of bizarre dreams and I began to scream as loudly as I could. Somehow, something or someone was choking my throat or it felt like it. 
I finally woke up in my room again, and I was profusely sweating. I looked at the clock to see that it was five o' clock in the morning. I went to the dining room and gulped down another glass of water. While drinking it, I kept thinking, "Am I still dreaming?"