Mis-shading in mcqs

Seniors who gave As, I need your advice please.

I finished my CIE As exams this June. Time's very short during MCQs so I was in a hurry while solving them. Despite being satisfied getting most answers right, I'm worried I shaded the wrong bubble in the omr sheet. This acc happened once in each of my bio and chem papers and I corrected it. Now I'm feeling like there must have been more mistakes I didn't get the time to check the whole paper.

Is this a normal feeling? Have Any of you here felt the same way and ended up getting good marks in mcqs. Please let me know