I agree with PrintDriver and Steve_O.
Years ago, I faced much the same decision as you. For two years, I was a physics major. As electives, to fill up my schedule, I took an art class and loved it. I took a graphic design class and loved it even more.
Instead of schoolwork consisting of memorizing stuff (like in my science classes), my homework consisted of creating things, which was a whole lot more fun.
I switched majors and never looked back. I’m also (mostly) glad I did it.
However, after graduation, it was tough. The pay was low, and the job security was non-existent. After about ten years, as I worked my way up while watching everyone else drop out and find other jobs, the pay finally started being OK. Even so, it still wasn’t anywhere near as much as I might have made had I stuck with the STEM route.
I’ve had a forty-year career in this field, and once I got established, it was good — sometimes terrific. Today, the field is oversaturated with design graduates and facing competition from ultra-cheap crowdsourcing and online do-it-yourself design services. The field is in something of a state of change (or chaos) right now.
The chances of making a go of it aren’t in your favor. Your artwork is nice and shows lots of artistic talent (seriously, it does), but it’s not graphic design, and many artists can’t make the transition from art to design. They’re similar in some ways, but very different in others.
If you’re stubborn like me, and if you refuse to listen to reason, like me, and are just dead-set on pursuing graphic design (like I was), I certainly understand. If you’re dead set on it, great. I wish you the best of luck. With enough dedication and work, you just might make it, and it will definitely take those qualities to pull it off. If you’re wavering at all, though, stick with the STEM thing and look forward to making some money.
I live in the U.S. Where you live, things might be different.