You might not be terrible at math. I thought I was terrible at math (I'm also a software developer). I also thought I was only good at discrete mathematics (which was a course I took during my university degree, heavily related to programming and CS). Furthermore I thought I was terrible at learning human languages, after having had 7 years of compulsory French at school and not being able to form a coherent sentence in French.
It turned out I was wrong on two counts:
A while back I started learning Spanish. The way I was being taught now was in a fun and easy way. I was also self motivated. In six months after starting, I could actually use some of it and knew more Spanish than I did French from 7 years of French lessons. 14 months after starting I was giving a technical talk in Spain (with an admittedly terrible accent and many grammar errors). Later today I'm off to Spain to help organise RetroEuskal with a bunch of Spanish friends. I started learning Spanish in my mid-30s, not as a kid. I learned it far faster than I would have as a child.
More recently I realised I needed better mathematics skills to be able to do more complex things in my electronics hobby, so I took an algebra course on Coursera. At school I had pretty much flat out failed algebra. In fact I was put into the lower maths set with all the thick kids (where you could only score a C at most in the GCSE, the exam we take at age 16) because both myself and my teachers were convinced that I was bad at the subject. But doing algebra in a course that was interactive, fun and gave instant results - I passed that with a distinction. I then did a pre-calculus course, and passed that with a distinction. I then did Jim Fowler's (Ohio State University) calculus 1 course on Coursera and passed that with a distinction too.
So it turns out that I was wrong about myself. In reality I was not bad at maths nor human languages. Now I admit I will probably never be a mathematician or linguist, but I can now do two things I never thought I ever would be able to. The reason I never succeeded at these things at school was because they were taught in a very boring and overly complex manner, and I was also pathologically lazy and didn't pay enough attention. The reason I succeeded now is due to having more motivation to do it and being exposed to teaching methods that inspire, and that aren't just hours of boredom.
Furthermore, while I don't usually use calculus or algebra in my day job, I have found that learning these things has improved the way I approach a problem.