J.F.
St. John's Wort helps some. My doctor suggested that I start taking it about a week before my period starts to help with my extreme PMS. I usually stop taking it 2-3 days after my period starts. It really does help if I remember to take it consistently, which is my problem.
I feel for you. My PMS got so much worse after DD was born. I can tell when the PMS starts because I have trouble concentrating, get irritated extremely fast, have back pain, bloating and I'm revenously hungry. I know as soon as I catch myself snapping at DH and DD what's going on and it's always confirmed when I look at the calendar. I think I need to set up a reminder on my phone to let me know when I need to start taking my St. John's Wort so I can try to catch it before it starts because it really helps me.
*ETA: I also appologize several times to my DH for my behavior while I am PMSing. He's so great. He never even complains. I wish I could just not behave that way but I just can't stop it.