Was pre-med but I want to do sales and trade now...possible?

SHORT VERSION(not much details though):
I was going for med school and did everything surrounding it but changed my mind to do business. Really like Sales and Trade from the looks of it but can't transfer to business school because I have more than 90 hours. Most of my classes have been biology, chemistry, and math. What should I major in and what would be the chances of getting an internship for sales and trade?

Long version and everything explained:

Hi guys,

so I've been reading a lot around here and at the moment I believe that I have hit rock bottom(but things always can get worst I guess) so I decided to sign up and ask for some guidance.

I wanted to go for med school and I've been doing good/okay. Did couple of researches, worked in labs, had a pretty good GPA(I explain this in a second), have had the same job for 5 years...took a second or even third job during summer time, changed my whole life-style and went from obese to a bodybuilder, was head of sales for couple of supplement companies, helped a company(actually two) grow bigger by setting them up with the right people, and did sales for supplement companies/research companies/and online store supplement store while was a full time student(this is on top of my other retail job, best buy), and even had great things to wright an essay about for my applications(went back to home country for the protests and lets just say it was insane...fun, motivational, but insane...life was on the line a pretty good amount of times).

Yes I got carried away with the jobs but I kind of really enjoyed doing it and had a good enough set up that sales would generate even If I didn't work for couple of days or even a week or so. But I only worked one retail job when I was doing this.

But here is my problem. During the end of my high school years they tested me and discovered that I was Dyselxic and ADHD and all that(my school use to blame my difficulty to learning on me being a foreigner even though I could speak English fluently and all that). Well recently my I have been taking ADHD medication(giving them a shot again) to help me concentrate(I was actually tested for these...like the tests that cost couple of hundred dollars not just lying to my doctor type of a student) so I could keep up with my classes since I've been taking a lot of hard classes at once. The problem is that they give me depression(suicidal level) but without them I can't keep up with all these classes. Well this is a problem because med-school is about ten times harder.

So I decided not to go for med school and I'm considering doing a medical with draw from this semester because of all these health issues and depression has effect my grades, by A LOT!

Well I love the business world and I am extremely interested in sales and trade but I have read that the request for them might be going down since computers are getting so advanced but I don't know if I could see that happen at the moment or even in the next couple of year but then again it's computers and from working with them for years I could also see it happen...either way that has gotten me kind of being worried.

Now here is were I'm screwed. I can't transfer to the business building at UT in Austin because with this semester I have 126 hours(changed major couple of times) and without this semester I would have 111 hours. So what should I do? Get a major in biology or chemistry? Because I see a lot of people doing finance for sales and trade and I don't know if I would have a good chance of getting an internship if I have majored in biology or chemistry. I do have a lot of math classes though (including trig, cal I, II, III, and differential equations) but it's been a while.

Have asked a lot of people in the business building at UT about sales and trade and nobody knows anything about it...even the MBA guy that I found on their website that was over it :(