I'm sorry your going through all this so young. It can be really confusing at times.
Every time I have taken an anti depressant I have ended up very manic within a week. But I've not really experienced being up and down so quickly unless I had a lot of environmental stressors going on in my life.
I have bipolar type 1 with rapid cycling. My manic episode will usually last from two weeks to a month with medication, longer without meds. However everyone is different, and different types of bipolar, different types of cycles.
Have you talked to your psychiatrist about this? Do you have a psychiatrist or do you see a GP ?
Have you talked to your dr about feeling suicidal? It very well could be the anti depressant making you feel this way, or if it were bipolar then being on an anti depressant alone with out a mood stabilizing medication could also cause your mood to cycle.
Please talk to your doctor about this like asap! These issues are both very treatable, it could be as simple as a medication adjustment for all this craziness you are suffering to stop.
But you
really do need to talk to someone about feeling suicidal.
Keep up posted on how your doing