I am sorry you are having mood swings. I know how bad it can be when you don't feel right and you don't know why. People can ask what is wrong, yet you don't know and that can be frustrating. If I may give you some survival hints...
1. Don't believe you are any less of a Christian. Sometimes, Christians ignorantly say things like "Just pray about it." or "You shouldn't be depressed... where is your faith?" Don't even try to justify your feelings to people like this... they don't get it, they can't understand... use your energy for taking care of you.
2. Try to find people who do understand. It's hard, but there are rare exceptions. People who listen without trying to 'fix you' or expecting you to get better within a day or two. Depression and mania are continuous- if you've had 3 major depression episodes, you're a lifer, Baby. Knowing/accepting this can help you prepare for next time.
3. Know that brain chemistry has a lot to do with mental health. People who say they don't want to go on medication have that right... and not everyone needs medication. But when the feelings of hopelessness, despair, and lethargy interfere with activities of daily living, one must decide what truly matters.
4. Take it one hour at a time. Know it will pass and try not to label or analyze why you feel this way... just take it one hour at a time.
5. Know Jesus is with you. You are never alone.