Marta, I've endured clinical depression since I was 13 or 14, but I didn't begin taking medication until my early 30s. After several years, Prozac stopped working so well for me, and I was switched between three other meds before settling on Cymbalta, Prozac's time-released younger cousin. It's been good for many years now, and it helped me understand I have manic moments, too. What helped me most was attending weekly local DBSA support group meetings.
Here's a link to their web page. Attending these groups for weeks helped me understand my experience was much, much better than many others. It put my problem in perspective and showed me my manic and depressive symptoms were relatively mild by comparison. The other great thing that happened was one night the person sitting next to me had a complete meltdown and I was able to help her greatly simply by being there and holding her until he feelings settled down.
Group and individual therapy is no substitute for proper medication, and it seriously helps you appreciate the need and desire to feel better. Ask your GP for guidance about bipolar/depression, and it is likely they may refer you to a psychiatrist who will prescribe medications. Also ask them about recommended therapists, who can help you sort through your symptoms and feelings about them.
I hope you get help for this. It's a terrible thing to endure, and help is available in many forms. Sometimes, the most difficult part is simply acknowledging that you need and want to receive help. You've done that here, and I wish you success in getting help with it.