Before I Stop Again

I have had depression numerous times over my life so far - Most times, when I "feel" right I don't need to take the prozac anymore and I am fine for months, sometimes years...  This time (1 1/2 mnths) It came back head strong & full force...  I am more irritable, impatient, really don't give a damn about anything and I am SO tired of being tired...  I had been taking the weekly Prozac for a little over 6 months when I stopped (okay'd by my doctor) I feel like I'm on a merry-go-round, now that I'm 40 and pretty sure I am pre-medipas; is this adding to it?  This time I have also had some rather mean, irrational thoughts (not suicidal) it's all apart of feeling...  lost, unappreciated, tired - I really don't know how else to explain it.  As of today, I have started retaking the pills.  I just want to know, seriously, does it ever go away...  What's next...