Oh, you didn't offend anyone. Let me take all the subject matter out of your OP and look at the skeleton that is left.

1. I am 17.
2. I made a decision A which I plan to implement for my entire life.
3. Nobody forced me to make the decision A.
4. No act of nature has made the choice A my only choice.
5. I find it hard to live with the choice A.
6. Most people in my age group would not make decision A because most people in my age group do not make lifelong choices and committments.
7. Now I want help and support accepting the choice A. Not pity, now, but help.

As you see, this way it is obvious that the source of your trouble lies within you, which is good news because you have the power to change the way you make decisions. The unifying theme that runs through most of the responses you got is "do not plan so long term and do not make decisions based on grossly insufficient information, but let life unfold, play it by ear as you go, and make adjustments to your plans based on new data as it becomes available."

You can also ask yourself whether you tend to plan too far in advance in regards to different subject matter. Do you know where you will be living in 30 years? What would be your first job out of college? Or if you continue studying, do you know which university will invite you for a post doc assignment? Have you started making plans for your funeral service?

If indeed you do plan so far ahead, then it would be interesting to find out why you haven't accepted that uncertainty plays a big role in your life. If you don't, then the question is why your thinking about relationships is such an oddball. Perhaps you can streamline your thinking process so that regardless of the subject matter, you allow for uncertainty, change in circumstances, change in your internal process, and...
...a bit of luck