-u posted exact same problem before joining university as well.
-eat more. eat healthy.
-study very hard. dont waste time on figuring out how to talk to women. Once you have your own money and everything, they'll come to you and WANT to talk to you.
-deny your "friends" any resources that you have. then the ones who start crying and getting angry are the ones you dont need. your true friends will be filtered out.
-with your best friends go to gym etc, have fun, talk to them. these are the ones who are gonna help you with your problem. spend time with them, do as they do (if its not wrong).
-if you think you've wasted money, ask your parents if they can afford to pay more for a change of field. (we cant do anything about that, thats completely between you and your parents). If they think its too much money being spent on you, then you have to stick to BBA. If time is a problem, let me tell you there is people who have wasted 10s of years and still done nothing. tell me if you need examples.
avoid people who are involved in wrong things, they look cool now, 5years from now, they'll be the ones in depression.
dont forget your religion.