How to understand music better?

I'm in an advanced music class at my high school currently and have just recently taken another test that has left me frustrated. I understand the theory that my teacher has given us (major, minor scales, intervals, triads, 7th chord etc). But we have recently started getting more into an analytical aspect of it with sonata alegro form, the sonata cycle and stuff like that, what goes into the form of a song. I get the terminology for the most part, lately I have been having to focus my attention on my other classes because my grades were slipping due to a massive project that my school makes all students do but it is very open ended so it is different for each student. So I haven't been able to focus as much as I used to in the class. I still work hard in it, it's not like I am slacking off and ignoring it. But I just have the damnedest time when it comes to analyzing something like Beethoven's 5th or Eine Kline Nachtmusic by Mozart. We didn't really do too much to transition into this. We did analyze a couple of fugues by J.S Bach when we were covering the Baroque era, and I understood that really well. But Even after she explained the terminology I couldn't follow along with the symphonies she was playing and it just leaves me very frustrated that I can't do it, yet just about everyone else in my class can, granted most of them either give everything to music and nothing to their other classes, or have studied for 8 years; but it discourages me because music has been one of the few things I am good at and yet it seems like everyone I meet is better at it. I'm not that good at math, I get B grade generally, but I have to work extremely hard for those B's, and I've lost complete interest in History after this year, but music has had me coming back to it over and over since I took a music theory class my freshman year (I am a senior this year), granted I had a hell of a time understanding anything in that class and the teacher really just gave me an A because I really tried hard and impressed him for a kid who only read tabs for the guitar at the time. As stated earlier I really get the theory portions but I have trouble applying it to a musical example, but I can pick up on it through Nobuo Uematsu's music sometimes (the Final Fantasy guy) and I get really happy when I can pick up on it. But it is just so discouraging that I can't do what the teacher wants when everyone else can and this is something I want to major in and I'm not particularly good at other things, mainly for the same reasons, but because I love music I keep coming back to it. Is there a way to really learn how to analyze music that is easy to understand. I am not looking for an easy way out. I am looking for a way that is easier to understand or something that will help me further my knowledge in a subject that I love, but discourages me when I fail to understand?