I went to a small liberal arts college. A friend and I entered as non-STEM majors and took the same intro to biology class geared for non-STEM types.
Well, she loved it. And switched her major to biology. And went on to get a graduate degree in plant biology. And still works in the field decades later.
So, no, it isn’t too late to switch to STEM. And it is okay to be undecided.