I liked some of the ideas you tried to convey purely through visuals, you seem to be developing an eye for that aspect of filmmaking.
From a purely cinematographic perspective, don't forget about your wide(r) shots! Even when you want to convey a lot of stuff happening in your lead's head, it's usually better to save close ups for the most meaningful moments. This could have used some 2-shots as well.
You did pretty well with what looked like available and natural light, I especially liked the darker scene near the end in his apartment where he is in the foreground looking camera right. Be careful about blowing out your highlights, especially when shooting with a DSLR, blobs of pure white from blowouts pretty much always look bad. You can get some of the same kind of material they use for bounce and diffusion at fabric stores, like muslin, which you can tape up outside a window or set just off camera to bring down the light level or fill in shadows. Bounced light can be surprisingly useful.
Double and triple check that your focus is right, especially if you have an AC to work with, bad focus is just lazy.
Watch your shutter speed changes, they were very distracting here.
Get your primary audio with a shotgun mic pointed overhead and down at the actors chest/mouth area, lavs should really be for backup when you can't get good mic placement since it's so much harder to make it sound natural without ambient sound. Room tone!
This was alright for a student film, keep up the good work. If I've been telling you stuff you already know, sorry, I know the experience of having someone on set trying to teach you things you already know like you're a child. As someone working in the industry it's always cool to connect with fellow filmmaking duders.