As your GP said, it's important to be cautious with antidepressants if you may have bipolar disorder. Sometimes it really is better to 'do no harm'. A lot of GPs just throw ADs out like they were sugar pills so it is good you have one who is more cautious.

The first time I ever took an antidepressant I ran straight into a manic episode about a year later, also for the first time. (I was also using cannabis to self-medicate which also played a role I think). The psychiatrists said that the antidepressant 'unmasked' an underlying bipolar but I don't that I would ever have been so ill otherwise. I just remember feeling incredibly agitated for a long while before I lost my sanity...

The most important thing in my mind, which is not what happened in my case, as I was misdiagnosed initially with 'somataform disorder' for chronic pain by the first pdoc i ever saw... is to find a good psychiatrist... one with experience in bipolar and depression... someone who has good reviews, lots of experience and whom you can trust and get the right diagnosis.