I feel for you, definitely know what it is like!
As for potty training, it is so true that the child has to be ready. Don't beat yourself up because he is two! Some kids are ready by then, but the majority are ready closer to three. I bought a small potty and had it in the bathroom what felt like forever. All our efforts at trying to get my daughter trained were useless. When she was close to turning three, we had given up and barely talked about it. Then boom. Just like that she said "I want to use this potty now" and she was trained from that point on. What I realized was that she was going to do this major developmental step on her OWN terms, when she was ready. As other posts stated, just forget about it for a while, and give yourself permission to NOT feel guilty about it!! Your son will do it in his own time.
As for you as a mom and student, I know how that is!! It is so hard to try and be a good student and keep up with all the work, and tend to children and make meals and clean the house and pay bills and do laundry and spend time with your hubby. I found, for me, I had to change my whole mindset and way of thinking to be able to get through it. And I know what it feels like with the guilt. It is overwhelming guilt! But, I had to make choices or I know I would self-destruct. For example, I had to let a lot of my ideas of how clean I want my house to be, go out the drain. I realized it wont kill us to have a messy house. And whenever I get a week or two off, I clean then. I had to let go and most of all, not let myself feel guilty about it! That is the worst feeling, it can eat you up inside. Second, I also had to let the guilt go about my daughter. No, I am not always there when I want to be. But I make our time quality time. And when I finish school, I have to realize how much better we will be for it. I am honoring my dream, and that will teach my child that even as a parent, it is so important to honor your dreams and goals. Eventually, she will model this behaviour.
You are doing the best you can, and the fact that you care so much proves that you are a great mom! I wish you all the encouragement in the world and the strength to get through this time!!!