depression?

I am 27 weeks pregnant with my second baby. My husband works out of state and has been for the last 4 years even before I had my first born, so I should be used to it by now. I'm pretty much doing everything on my own, while raising a toddler. Lately I've been so down and sad all the time. I know it's part of being pregnant (hormones) but it's more than that. I cry all day every day worried to death that my husband is going to leave me or find someone else while he's away. I am so in love with him as he is with me. And I could never see him doing that, but it's just been on my mind a lot lately I have dreams about it and cry constantly. I've never felt this way before. Idk what to do anymore. Any help would be great. I feel like I can't talk to him about it. But I need to talk to someone. Is there something wrong with me? Please help! I hate my three year old constantly asking me if I'm sad and why I'm crying. It breaks my heart but I can't help it :(