Sciatica

I've ways had symptoms of sciatica throughout my life, pretty much since I was a pre-teen. (I'm 28 now) Today it has come back with force. I am having severe symptoms of sciatic never pain, intolerable. I can hardly walk without collapsing and the pain is excruciating. I have an appointment with my OBGYN tomorrow for unrelated reasons but will definitely be discussing this regardless. My question now is, can I use a heating pad until then?! This has to be one of the worst episodes I've had to date. The pain is constant and will not subside. Help!