Lou Talman says: >Before you make a decision, you should take an advanced mathematics course---one which emphasizes Definitions, Theorems, and their proofs.
Alternatively, master a course in computability theory and understand the theoretical basis of computation as initiated by Alan Turing and carried on by some of the smartest CompSci-mathematicians in the last 80 years. These courses are typically proof and theorem based and some prior exposure to that style is very helpful, so as you don't miss the train for trying to understand the schedule board. Most Comp Sci majors in my experience suffer through such courses. If it turns out you like it, I would say you have interests that really do straddle the two disciplines. You might also look into algorithmic information theory and Kolmogorov complexity (at least read the Wikipedia pages on such topics and follow the leads.)