Linguistics ! If you want a mix of 'alpha' (as in, humanities) and 'beta' (as in more exact sciences), linguistics is THE field for you. If you are currently doing computer science, you should have the required level of abstract thinking for it.
It's a bit hard to explain what linguistics is all about. What it is NOT, is English, or any other specific language. Not in the least. It is also not one of those courses you have to read a plethora of books for and write countless of papers, which is something I personally loathe (it is some more for some subjects though).
What makes linguistics fun, is that it discusses language and ALL it's aspects. This makes it a very broad major. Speech technology (which is more science-like), syntax (abstract treatment of grammar and 'deep structures' of a sentence, something you'll probably enjoy because you currently are doing maths and computer science), phonetics (the study of all possible speech sounds, pronounciation and recognition of them), phonology (how 'phonemes', abstract units of speech, are realized differently in different positions, how they behave etc.), historical linguistics (sound changes over years in languages, general sound-change processes), psycholinguistics, neurolinguistics, semantics.... there are so many different fields. Though I do not find all of them exciting, there is almost always something in there that will grab your interest.
Carreer-wise, research is the most obvious way to go. Researching an unknown language, speech-technology research, neuro- or psycholinguistic or syntactic research... But linguists are probably wanted for any sort of job positions, because for a non-exact-science they will have a high level of abstract thinking.
You can also go the comparative linguistic route. You will probably learn more languages (at my university they offer Middle Welsh, Lithuanian, Avestic...), there's a higher emphasis on historical linguistics and historical research is the more obvious way to go. But I generally have the idea that general linguistics (not necessarily generative !) offers more opportunities later on.
I'd say, look into it, wiki it, visit some open days etc. I also know plenty of people who do linguistic subjects next to their main study (maths, physics, african language/culture...)