Don't feel bad. I dropped out of high school. Years later I went to college. My math testing scores were horrible. I also had to take remedial English classes. I had to redo elementary algebra (just a step above pre-algebra) three times because I just couldn't perform well when it came to tests. At one point I thought I wasn't going to be able to even get to college algebra and entertained dropping out of college.
My mom also struggled like I did in math and urged me to stick with it. So, I kept at it until I finally was able to squeak by in algebra. I started also in fundamentals of English. I later graduated with an English Ed degree.
One of my suggestions is to try and narrow down a major coming into your junior level or after having around 60 credits under your belt. I graduated with 186 credit hours over an 8 year period with only a bachelors degree. Focus to some extent is good.
Another suggestion is if you have extra money left over that you don't need to spend on books or school related artifacts, put it in an interest bearing account. Let it sit until the end of school. If you have any loans or anything to pay to the school, pay it off.
Last suggestion (as has been mentioned) is pick your classes and hours amount wisely. Spread your electives and fun classes in with your hard(er) classes. Look into online classes. I took a few classes online that were just absolutely awesome (meterology, advanced composition, health and wellness). 8 week classes are also pretty cool. It's a way to get two classes done in one semester which would've taken you two semesters.
I think that's it. Those are my suggestions from experience.
p.s. Have fun with your university years.