If you want to be an engineer, you're going to have to resolve your issues with math. Almost all of engineering and most of science is based heavily on math. That's probably not what you wanted to hear, but you're only in 6th grade so you have time. If you really want to be an engineer, and have the drive to make it happen, you've got more than enough time to catch up on the math. Do some work over the next few summers and you should be in good shape.
I'd recommend getting to at least calculus by the end of high school. Engineering schools usually require 3-5 semesters of advanced math, and calculus is just the first semester of that. If you're not already prepared for that, you'll need to add another semester or two of remedial classes before you can get to your required classes.