See if you can make the problems more concrete.

I would get or make a calendar for the next 18 months, for example (two?) and put various personal dates on it that are relevant to your best friend; maybe mark what day you will write every couple weeks and, when you receive a letter, put that on there? Just use the calendar for your friend, to represent the time apart and how soon they'll be back, etc.

Take a moment to write a schedule of your classes, what they are, what homework, papers, tests are left, where you are and how you'd like to do. Get it outside of your head so it isn't just swirling around and so it can be uncoupled from the money issues.

Make a budget for each of the next 4-6 months and a projection for the next year or two; see if you can free up some money so you are not so crunched if you have to take courses in the summer and also make sure that makes sense rather than adding a course or two to the Fall courses instead or putting off the student teaching; taking things slower until you don't have so much going on elsewhere.

Look at the porn use, maybe use your "friend" calendar to work with it and mark its use on there? Thinking about your friend might help with not using the porn? But start recording your use of it and keeping track; with it just "there" it can seem more/less than it actually is.

Get a handle on each problem you have and write it out, get it out of your head where you can see it.