Partner with depression

Recently my partner has been slumping into a depression. I don't know what to do. I feel so lost. I want to help him but he laughs in my face and just won't let me in. He won't go to the doctors (he's as stubborn as they come) and when I suggested it he said "why? I'm not poorly" and stormed off. His mood swings are seriously affecting me and my migraines are returning full force not to mention how it's affecting my other health problems. 
Have any of you got/had a partner with depression or can give me advice on what to do. I'm almost at breaking point!