depressed and don’t know what to do

i’m 17wks pregnant and a couple days ago my depression hit me like a ton of bricks. i’ve had it since i was younger and am on medication for it but it hasn’t been this bad in a long time. i have cried so much. it has me questioning my relationship with my fiancé (who has been nothing but supportive and i love him very much) and im just not happy in general. has anyone else dealt with this during pregnancy? i feel miserable and so guilty for feeling this way. i see my new ob at 20wks but i can’t do this for three more weeks. i feel like im drowning and it won’t get better.