I suggest working your way through the lower division mathematics requirement that a college CS major might experience. Course material is one way (just make sure to actually do the homework), taking courses at a local university (or even a good community college e.g., in Silicon Valley De Anza and Foothill Colleges) is another (make sure to find an excellent instructor for Calculus and to take a discrete mathematics course).
The other part to keep in mind is that there's different types of software engineering roles and different kinds of mathematics. Some (e.g., machine learning and data mining) are very mathematically intensive (to understand some papers, you'll need to do integration by parts), others (e.g., graph theory) are more about discrete rather than continuous mathematics, yet others (systems programming, application development) are least mathematics heavy (and where they are, again, the math is mostly discrete rather than continuous).
