I keep feeling sick during the day and night?

About 8 weeks ago i started to feel a little sick during the day and worse at night. there is nothing that clearly causes it. It gets worse at night as i am laying in bed and i almost have a panic attack trying to calm myself down because i think im going to be sick and i hate being sick. I went to the doctor and they thought it could be something wrong with my reflux and the acid coming up my gullet making me feel sick. However the feelings continued despite a course of tablets so i went back to the doctor, my doctor then sent me to the hospital to be checked out. The hospital kept me in over night and did both blood and urine tests but came back with no answers and said that i was healthy. i am now lost for answers. i just want to know what is wrong with me so i can fix it. can anyone hlp me. i've never had anything like this before and until this came along was the first time in 8 years i had been to a doctors and my first time in a hospital. Please Help?