You have led an extensively stressful time in your life.
I am very sorry regarding the death of your sister, as well as losing your mother's S.O this weekend. That is really hard to deal with ~ especially with a bipolar parent!
It's very natural to begin questioning everything in life after experiences such as these!
Especially if you're still a "child" or "teenager". Because, in these phases of life, we haven't found ourselves yet. It's very common to question your worth, the meaning of life, and where you're headed in situations like these.
Whether or not you're doomed to a life of misery ~ I certainly HOPE not!! I don't think that you are. I do think that things are going to be tougher for you, than a lot of other people, but I think that you can make it. Regarding your question of normalcy...that's a toughie for me.
I think that we can still live productive lives, mentally and/or physically ill. But we have to push ourselves harder. We have more complaints and general dissatisfaction. We also have more to be proud of ~ for all that we've overcome in our work! That work doesn't stop. It isn't ever "easy", but things do become more manageable at different times in our lives. We aren't doomed to failure!
We need to reach out in the tough times and get help from others sometimes. Imo, professionals are the most helpful. {I have a general mistrust of people, I guess.} They're the ones that I depend upon (as well as several friends that I've made in here actually) when I really can't find the motivation to keep going in life. They get me through to the next bump, and so on. That's just the way that it is. There are some sweet moments of satisfaction and enjoyment though. Some beautiful times that make life more meaningful. And that does help.
to you!