Birth Control Emotional Low?

I am on low Birth Control and have normal emotions throughout the month, minus a few days on my period. However, since getting on Birth Control over a year ago, every 2 months or so I go through what I can only describe as a Depressed like Emotional Low. Full on hysterical crying, no energy, outburst of frustration, like I'm a totally different person. Even my husband can tell. And I know when it's happening. I can feel my emotions plummeting. Then after 3 days of a slow down-hill I hit rock bottom (hysterical crying for little to no reasons, etc)

Ummm is this normal?? Is this because of my BC? Is it something completely different? How do I stop it from happening because it feels like an extreme case of depression.