Callie50 is right. If you want to run a small business, then set it up as a small business. As well as registering, you should write up a business plan. This is not as scary as it sounds, but it will take some time and research. There are serious advantages to doing this.
1. You will have to work out the taxation and ALL other costs, and determine whether you are making money.
2. You will have to get your head around the money in/money out cycle. Know this: the one thing that kills small business more than any other is cashflow (or lack of cashflow). If you are owed lots of money through invoicing but you haven't got enough cash to pay for the stock you need you are in trouble. And if you haven't factored in enough profit, the cost of borrowing will send you to the wall.
3. You will probably uncover more products you can add to your inventory (have a look at www.alibaba.com
4. You will be more serious because you have put some serious research into it.
Yes, you can run a business without a business plan, but you are a student and not afraid of a little research and thinking about things.
There are a lot of other benefits to creating a sound business plan, not least of which is that it becomes a powerful asset if you ever decide to sell your business and start a new one. It also helps if you ever need finance (banks will usually require that you have one).
If this is the first time you have ever created a business plan, expect to spend a good 20 hours or so on it, maybe a little more. Don't stress, it is the BEST investment you can make in your business.
And if, through your planning, you decide your business idea is not viable, and you can't change it to become viable in a way that the market will accept, WALK AWAY.
You are obviously smart and entrepreneurial, there are a gazillion business opportunities out there, with more coming up every day as business gets more digital.
I hope this helps.