When a cancer guy crawls into his shell?

It sounds like you two live in different cities. Long distance relationships are hard. Too many things to interfere. He may not be going into his shell, but is probably busy with work and if he attends school also then his time is taken up not to mention you live in different cities. When my wife and I were dating we lived in different cities, but only 35 miles apart. That was tough enough. neither of us were going to school so work was all we had going on. I found myself driving that 35 miles several times a week just to spend a few minutes with her at her work on break. We have been married now 16 years.