It seems that after the spill the home button is constantly sending a signal that the home button is pressed.
First thing to do is get your phone open and assess the liquid damage inside the phone (especially where your home button is). If you notice any corrosion or liquid in the phone I would fully disassemble it clean up all the components with 90%+ isopropyl alcohol and a soft bristle brush(tooth brush). Once the the components are clean and dry reassemble the phone. I would also look into replacing home button.