This sort of question is difficult to answer here. It's the kind of question that is best suited by a series of back-and-forth interactions with a trusted mentor (or, failing that, a trusted psychiatrist or similarly trained professional). The best that I can offer in this format is a few independent answers. You are free to amalgamate them as you see fit, and if they help you, then good. If not, they're just text from a stranger. I will, however, try to tie it into philosophy, since that's the forum you are asking on.
Answer #1: "Fair" is an F-word and a four-letter-word, and should be treated accordingly
Of all the answers, this is going to be the most brutal. An expectation of fairness is the enemy of happiness, and you used the word "fair," so I'd like to challenge that one first. The other isolated answers will be less combative.
Personally, I find the concept of "fairness" has a strong tendency to lead to negative feelings such as suffering. It has been found that other primates have some concept of fairness, so it is clearly part of our psychology, but it's a troublesome one. Fair implies that there is some cosmic equality. Unless you have a religion which supports that, "fair" has a strong tendency to get you in trouble. It is remarkable how little of the universe seems to fit our concept of fairness, so an expectation that things will be fair has a strong tendency to lead to unhappiness.
We have a tendency to look to those that are happier than us when we invoke "fair." You, yourself, did this. However, we do not often consider those that are less happy than us. I don't know why we do this, but it seems to be a pretty reliable general trend. For some people, seeing those who are less happy than us is a useful reminder. If you happen to be one of those people, consider this father. He's a Pakistani immigrant, trying to make a living on the streets of America by selling pens. I keep his picture around to remind me of... something important.
Answer #2: It doesn't matter if life is predestined
There is no reliable argument proving that life is predestined. Some religions will argue that everything in life is predestined, but they can only argue it if you start from assuming that religion has the Truth. If you find such a religion, feel free to believe it if you wish, but there's no obligation that everything be predestined.
Even if everything is predestined, that does not imply that the path you are on cannot change. For an exercise, consider the stock market. Go find some historical records and find trends in the stock market. Pick a few trends you think always hold true, and then fake invest in them. By "fake invest," I mean follow the stocks in future months and see how much you would have made if you invested in those stocks. (For actual investments, obviously you should not follow an internet stranger's advice, but for fake investments, it's safe).
What you will quickly find is a well known adage in the stock market: "Past performance does not predict future gains." A path that was only making money in the past can turn into a loser in a heartbeat. A path that was losing money like crazy can suddenly hit it big. Yes, there are patterns, but nothing says that the future needs to follow them. Indeed, environments such as the stock market demonstrate that complex systems (like humans or stock exchanges) regularly break trends and do something unexpected, for better or for worse. There is no guarantee that your current unhappiness can only lead to future unhappiness. That's a good thing!
Likewise, past unhappiness does not automatically imply future unhappiness. I will admit that there's a statistical trend that way, but that's nothing more than a statistical trend. If I may suggest the movie The Pursuit of Happiness, it is an excellent dramatization of this.
Answer #3: Whether suffering can end or not is a question philosophers disagree on.
This answer is probably most directly focused on your real question: we don't have an agreement among the philosophers as to whether life is suffering. We can see this disagreement quite clearly in religion. Buddhism is built in the tenant that all of life is suffering. The Sanskrit word used here is "dukkha," which has its roots in the idea of a wheel with a poor axle hole in it, thus creating imbalance in life. The Buddhists claim that the only way to escape dukkha is to follow the tenants in their religion. Other religions suggest that the exhalation of their particular deity is the only way to escape suffering. In fact, the tendency for religions to suggest that they can end suffering should be treated as a hint that it is not unusual to feel that life is suffering.
Indeed, one challenge in philosophy is to define what "suffering" really means. We often have an intuitive sense of it, but putting it into words can be a real challenge.
Answer #4: Consider biological causes
I'd be remiss in this day and age, with all its scientific advancement, if I did not mention that what you describe can indeed be attributed to chemical effects within the brain. As a random internet stranger, I am not in a position to diagnose you, personally, but it is recognized that these feelings can be caused by chemicals. There are people who can help you determine if there are biological or chemical causes for your feelings, many of whom have degrees in psychology or psychiatry. Such is also beyond the scope of Philsophy.SE, but if you feel it is worth pursuing, there are people who can help you study this side of the story.
So what should you do?
I don't think we can say such things, as random internet strangers. Some would say to give up trying. Some would say to try your hardest, despite the odds. Some would suggest strange middle grounds, like Wu Wei which is a Chinese concept of "doing without doing" which refuses to be categorized into a simple "try or don't try" scale. So while I cannot suggest an answer to what you should do, I can point out that there is an extraordinary and beautiful range of answers to "what should I do?" The one thing you should not feel is hemmed in and forced into one answer -- there's so many answers out there.
