Suggest Medication For Lower Back Pain And Neck Pain

Hi I am 26 years old almost 5 years ago I got my tubes tied.I am 193 lbs. Just last monthI was 182 I am now having pregnancy symptoms. I am nauseated, have heartburn where it wakes me out my sleep, constant urination and I have also gained 10 pounds within the last month. I am experiencing lower back pain and severe neck pain. I can't sit up for long periods of time and am very uncomfortable. I have taken numerous pregnancy test and they come back negative. I am about to go crazy because I don't know whats wrong with me. I feel flutters in my stomach every now and then and pressure on my pelvis..I never missed a cycle but this month is was heavy for 1 day and was very light for 2 additional days. Could I be pregnant?