I have been diagnosed with severe depression, how long do I need to stay on these medications? I hate the side effects.

Unfortunately, most patients with depression are at a risk for relapse and thus long-term treatment is required. In general, patients with depression are usually assessed each year and the doctor then decides whether to continue the medication.

The current custom of clinically prescribing continuous antidepressant medications is to prevent relapse or recurrence after the third lifetime episode of depression. Other individuals who also require long term anti depressant treatment are those who have had two episodes of depression within a five-year span. If for any reason, the depression was severe enough that you attempted suicide or caused some type of self-injury, then long-term maintenance is required after just one such episode.

In the USA, most psychiatrists continue the medications for life and evaluate the patient regularly. 

You have to understand that if the doctor stops your medication and you hurt yourself or commit suicide, the doctor is in big shit with malpractice lawsuits.