Need advice

I really need some advice or something. I’m 7 months pregnant and I have really bad depression to the point to where I don’t even want to be alive I haven’t thought about hurting myself or anything like that. I just feel like my 2yr old son and this new baby and everyone else would be so much better with out me here. I have no one to talk to not even my fiancé cause I’m afraid it’ll start an argument and I’ll just get worse. I really just need someone to help me or try to explain what I should do.