Depression while pregnant.

I usually have anxiety and depression normally but when I found out I was pregnant I felt like it disappeared. I finally got to experience what I wanted most In this world and I have been over the Moon with everything it comes with. I have been moody here and there and cry over spilled milk but I wouldn’t call that depressed. Anyways I’m 6 months pregnant and now suddenly I woke up sad for no reason. The only thing that gives me joy is thinking of my baby boy and how much I love him but when I think of anything else I get so sad. I’m happily married, have a great job, live in a nice apartment. Sure things can always be better but I’m blessed for sure! So why do I get these intrusive thoughts and sadness that just overwhelms me😔. It makes me sadder because I haven’t felt this way in 6 months and I was honestly knocked off my cloud. 😭