I'm 19 Years Old And I Have Been On Depo

I'm 19 years old and i have been on depo provera for 4 years and with in the last month i have gained 3 pounds (without eating more than usual), i have been nauseous nonstop for about 2 weeks, ive had frequent urination, abdominal cramping, and headaches. i have taken a home pregnancy test and its negative but i dont feel like its correct because i have never felt like this before since ive been on depo provera. Please help.