Does it get worse before it gets better ?

I’m on day 9 of taking pristiq and for the first week I was on 25 mg now I’m on 50mg. I haven’t noticed any mental improvements only decline. I feel like my depression, anxiety and feeling of impending doom like I’m going to feel this terrible forever has gotten worse. I’m kind of expecting not to feel better since I just started but I’m worried this med won’t help me get out of this deep depression and anxiety and feelings of doom. How long does it usually take to notice positive changes and is it normal to feel worse before feeling better ?