My life is "falling apart" all at once?

So ... I'm finally going to college (university) and I was delighted to know I got sufficient grades to enter the university I wanted to go to... but I didn't get the top grades I expected and now I am feeling a little insecure with my major choice... my bf also has told me he doesn't want to live with me anymore and I am so worried because I know that I won't be able to focus if I'm not well with him... I wish I could not be dating at all.. but I did and now I have to live its consequences 😞 I am worried because I feel down, unmotivated and incapable... I only have a shot to pass the degree... otherwise it will be a loan to pay and no fucking major