Postpartum Depression

I'm going to discuss PPD with my doctor next week and I don't know how to tell my husband. I've been plowing through my days because if I stop to think I know I'm going to struggle to keep it together. It's been 5 months and this overwhelming sense of sadness is just starting to bubble over and I find myself becoming anxious and crying over things I know rationally shouldn't upset me at all. 
How do you tell someone you love that's your so deeply unhappy? That you've been hiding that your crying all the time? I don't want him to think it's his fault. Admitting to my family there's a problem has been my biggest obstacle in seeking treatment, I feel like I'm being weak and letting them down.