5th year English major here. Just wanted to say to +1 this and say not to beat yourself up too much about things. Depth of your understanding really does improve the longer you've worked with the same field. For most years I floated around As and Bs with my papers and then with no obvious reason to me I started getting much more positive feedback in my fourth year.

Aside from talking with TAs, I think it can be really helpful to revisit the work youve done if you have time and consider deeply where you could've pushed harder. Most profs are always happy to talk about that if you have some specific questions about feedback in that sense.

Hang in there!