I see. Well, you say you're "not that serious" about wanting to be a biochemist, but is it still something you want ? Since you also said earlier that you couldn't commit to something else three more years, to keep going in that track doesn't seem like a bad option.

Otherwise, if you find a work project involving one or several of the subjects that interest you, that'd be the other good option.

I'm a student myself, and I've jumped a few times from a study to another, but now I'm committing to physics and I don't intend to let go. But there's also a few skills and fields of interest I like learning on the side... That's not a contradiction, everyone is interested in different things and has a skill set that's doesn't depend only ln their work. I intend to be a good amateur artist and an informed layman on several subjects, but physics is what I want to study professionally.

Committing to something doesn't mean you should give up on all the rest, just that you should set boundaries on what will be the thing you'll be an professional in and the rest. Even if you go a different path, don't think of the time you devoted to biochemistry as wasted time... It'll have fed your culture and skill set. Maybe it'll be useful to you, maybe not, but either way it's not a negative thing. A choice is good if it is a choice you've made. And you're not that late anyway, some have "wasted" more years than that.

Of course, I'm just a student myself, not a teacher or anything. Beside, I'm French and our university systems might be a bit different, so take it with a grain of salt.