not sure how old you are but are you on b/c pills? That could be the reason for multiple periods....if you are on b/c, you may need to switch. I would definately call the doc on that.
As far as the Effexor side effects go, the first week or two it really mellows you out and yes, you do sleep a little more, at least it affected me that way. I am now on 75 milgrams and after a couple of weeks you settle into your old routine. Effexor has worked great for me, especially with the racing thoughts and anxiety.
Before you take another dose of Effexor, go to Google, type in "Effexor Withdrawl". Are the withdrawls of getting off Effexor worth the benefits of taking it? ABSOLUTELY NOT!
Now, go back to Google and type in "Natural Cures for Depression".
If what I have been thru, trying to get off of this Evil drug, stops just 1 person from ever getting on it, then maybe it's been worth it.
I wish I would have educated myself on what I was putting in my body, before I did it.