The mood swings may be caused by different things.
1/ a bipolar disorder or at least cyclothymia
2/ people who are not in the bipolar spectrum but are depressed can have these symptoms (anger/irritability)
3/ a mood disorder can be hereditary.
4/ hormonal changes (drop of estrogen) if you are on any birth control, it also depletes the body from magnesium (magnesium has a calming/anti anxiety effect) If you find yourself having the mood swings primarily around the time of your menstrual cycle, then if may be a case of PMDD.
The good news- mood disorders and hormonal changes are treatable easily with medication. Anger management can be learned during counseling or even hypnotherapy.
Your first step would be to get a face to face evaluation by a psychiatrist (possibly a female ) Then, you may consider having a hormonal panel blood test done by your OB. It would show if there were any hormonal concerns.
There had been studies that show that supplementation with Omega 3 fatty acids decreases anger/irritability and alleviates depression.
There are different options to address your concern (depending on what you would like to explore)
Hypnosis for Overcoming Anger (Hypnotic Empowerment Series) by Janet I. C. Decker and Hypnotherapys Services (Audio CD - May 17, 2007)