If your therapist sent a letter to your GP raising a concern then I would advise speaking with your GP again to arrange a referral to a psychiatrist for evaluation.
As LCC has said in her response it is very common for BP2 to go undiagnosed because the "highs" are not as extreme as in BP1 and they cause you less problems than your lows (although I am not trivialising the "highs" commonly known as hypomania in BP2).
It could be that you have cyclothymia another member of the BP family which is less extreme than BP2.
Whichever, it is important that you get correctly evaluated in order to receive the best treatment. Although BP can have long periods of time where you feel relatively stable it will always come back and bite you on the bum and you never know how bad the episode is going to be.
If you aren't happy with the outcome of your GP visit don't be afraid to go back and ask for another GP.
I'm sorry to hear you've gonet through a horrible time, you should be proud of yourself that you cleaned up! Honestly, and only my opinion, you should be on meds and sooner rather then later - mood swings, heavy depression and hypomania (moderate highs) are main symptoms of BP2, which is what I have. With a close to deadly suicide attempt, don't you think it's in your best interest to get on to meds? Find a psychiatrist that will help you. Be absolutely blunt and don't minimize your emotions and mood swings, that's the only way you can get help. Most folks don't see their pdocs when they are in their high moods, so the pdocs only think you are depressed. I was actively planning my suicide, when the lightbulb went on, and I walked into my local ER. They kept me for 4 days to ensure I wouldn't self harm, sent me home with a med that helped and set me up with a good shrink. Though that was the lowest period I'd had in a couple of years, I"m glad I went through that, so I could get the help I needed. If you think something is wrong, go with your gut instincts.