Masters in Applied Mathematics or Computer Science? Or a second Bachelors?

Hello,
Recently I Graduated with a BS in CS and a minor in Math. I wanted to double major in Applied Math and Computer Science but could not fit them both in in just 4 years and so dropped my Applied Mathematics Major.
I already have an ok job but I regret not finishing my Applied Mathematics degree. I feel it might have gotten me a job I preferred. ( I am in software development but want to be more in research I think).
I was only 4 classes away from the duel degree in Applied Mathematics but the college says if I go back now I need to go an entire 30 credit hours (a full year). Thats a long time to only get another BS and I hoped to get a Masters degree anyway.
Since I have a BS in CS I was looking into masters programs. Since the Math Degree I want I was looking into Applied Mathematics Masters but I feel I might be slightly behind and that it would somewhat override my BS in CS degree.
A computer science degree would further my career more than the Math degree would and the College I went to actually offers this degree.
I am not sure what to do. Am I being irrational for wanting a Mathematics degree?
Thank you.

First of all, if you were only four classes away from a dual-degree in applied mathematics, I highly doubt that’s the reason you didn’t get the job you preferred. Four classes don’t really make a big difference, unless they were four classes that are crucial for the research you want to do. (The other problem might have been lack of self-promotion. Just because you didn’t complete a formal major in applied math doesn’t mean that you can’t emphasize your applied math chops on your resume or in a cover letter.)

Second of all, if you are only four classes short, I bet you more than meet the prerequisites for an MA in applied math. I’ve seen some MAs in applied math that only required three semesters of calculus and linear algebra. It’s unlikely you would be behind much at all. Also, most MA programs in applied math that I’ve seen are 30 credits, too, and would take about a year full-time and a year and a half to two years part-time. Definitely don’t do a second bachelor’s - there’s no point. You’d spend the same amount of time and money and would come out with less value.

Now, as to whether you should do one at all? That’s up to you. If you’re only doing it because you regret not finishing the concentration, but you don’t need it, then I’d say don’t do it. That regret will go away after a while. If you want to do it because you want to change careers or advance in your own career, that’s a good reason. However, you have to decide whether an MS in computer science or an MA in applied math would be better. Both of them have good career prospects; it really just depends on what you want to do with your life.