The question is: why did you need ChatGPT to 'fix any grammar issues', when you have a perfectly good grammar checker on Word? Fixing grammar issues does not require generative AI like ChatGPT - which doesn't just 'fix grammar issues' but rewrites text from scratch, hence it is 'generative' as opposed to 'corrective' AI. To fix grammar issues stick to grammar check on Word and you can't go wrong.
As for 'making it sound smarter in a way', using AI to rewrite stuff doesn't make it sound smarter to your professors - it just makes it read sterile, stiflingly predictable, and like you've probably used AI. Your professors have been reading thousands of student essays over many years, they know what it looks like, and they can see when you've used AI even in the cases where they can't prove it - consider how you can intuitively tell when something is CGI in a film rather than actually there; it just looks fake. It's the same with ChatGPT. Using AI won't get you any brownie points with the marker. Even if they don't have concrete proof, it's not going to impress them, it's going to have the opposite effect. We want to see you thinking for yourself, not robotic polished banality. Writing is a form of thinking, not something you can outsource to a machine. Aspire to be good at writing, aspire to be good at thinking. Take pride in trying to be good at it. Give yourself a kick up the backside and don't do it again.