Hello,
I didn't knew where else to ask so I decided to try it here.

There are these moments specially when I'm feeling down (or sometimes even on normal days) when I get this really focused sense of perception and fear of my own death, my existence, the whole universe and the lack of sense and meaning in the world and I start to panic really bad. It is as if there is only one truth and it is that I will stop being. It happens more often and stronger during the night, usually when I'm trying to sleep. This happens to me at least since I was 11 years old. About a month ago I had a really strong moment like this, I think it was the worst ever because it lasted for two whole weeks almost non-stop and I couldn't calm it down or make it go away like I'm usually able to do by distracting myself with something, like TV or soft music. The two weeks were horrible and the only other time that can be compared is the first I remember that was when I was eleven, when I was trying to sleep but couldn't stop thinking about my dog who had died several weeks before and I realized I was going to die and started panicking my mother noticed me crying in the bathroom and I explained it to her she spent the whole night comforting me (sometimes remembering that one day my family must die starts one of these moments). For some time, I thought it happened when there were changes of rhythm in my life (end of the school year, end of vacations, big events) or whenever I left my comfort zone but there have been times when nothing major happens and I feel it the same.
Before the 'two week' incident, for about a year or so I've had been feeling down, feeling worthless, feeling sad and in a general way depressed (lack of appetite, lack of joy or interest in doing anything) but it was never continuous, I could feel like this in the morning and in the afternoon feel like doing everything in the world at the same time, and in the low moments I used to take notes on when I felt like killing myself and for some time I took a lot of notes but that feeling was only 50% percent true, in these moments of feeling suicidal I did 'reckless things' like putting a knife to my throat or driving recklessly but never ever hurting myself or putting myself in real danger. During the two-week episode one thing I realized was in how dumb I was and swore never to think like that again. I keep on feeling down, sad and worthless from time to time and the most annoying strong sensation of being uncomfortable, a bit out of place, lost, very... strange, in a way (the very extreme opposite of the sensation caused by a lit fireplace, a blanket and hot chocolate while watching Downton Abbey during a cold winter night) and very, very nostalgic about everything, even things that don't usually matter.
I think I might have depression and bipolar disorder. About all this I just wrote. Is it normal? Is there a name for it? Should I seek some sort of professional help from a psychiatrist?

A bit about myself:
I'm almost 20.
I believe I am naive, very naive, a bit like Monsieur Hulot (if you don't know him a man who never has bad intentions, who never sees evil in other peoples acts or intentions), the kind of person who believes in real love and the whole Disney idea of magic love. I like to think of myself as a gentleman, I avoid being rude to anyone, avoid conflicts and am usually very respectful to everyone, also I believe I am a man of culture, I [genuinely] like opera and classical music, literature such as Tolstoy, cult films like Tarkovsky and Bergman or Woody Allen but I also like a wide variety of music genres (not any sort of metal, rap nor popular music for today), I also like some best-selling novels such as the ones by Dan Brown and I also watch some of the blockbuster movies (those that are watchable). With this I'm not bragging if it seems so... Is just that all the friends I have are old friends and they are the opposite, I never had any friends with more of my taste or cultural knowledge to discuss interests with. Anyway, for the last year I've been at home in a sort of mandatory year of, mandatory because I didn't know what to do, and for the whole year I had very little social bondages (I don't like much to go out at night and if I do is to the cinema or a quiet café to drink responsibly and just relax whilst all my friends prefer the opposite, getting wasted and high listening to noise) and so I've been a bit isolated, not that I mind much, now I've decided that I will proceed my studies and enlist in a university, but have low hopes for my grades from high school were low and the whole 'what am I going to do with my life' stress starts again.