What's the highest math class you've completed? Several schools are looking for Calc I / Calc II, so you might open yourself to more options by taking a few math classes. I'd only take classes to raise my GPA that I'm sure I'll get a good grade in.
At my school, while it's not encouraged, it's possible to essentially audit the first class, then get the teacher to sign a drop/add slip & add the class after the first one. I audited the first session of a summer Diff EQ class & decided I would drown, so I didn't add the class. You might want to consider this option so you know what you're getting into - in my experience, as you get higher up in the maths, the less the profs can speak English. (Because they're speaking math & have apparently forgotten how to speak conversationally - I'm not making a nationality generalization.)
You might find science classes more useful in the future - why not take an animal anatomy class or something?
Your plan to raise GPA by taking additional classes is sound, unless you're applying somewhere that only looks at your prereqs for their calculations. You will be able to show that "upward trend" on your application that all the cool kids are talking about.
Can anyone confirm/deny math classes even count towards science GPA? I'm assuming the OP is referring to PharmCAS GPA, rather than a particular college's calculation.