Hey there Winchesteraddict.
You should probably read the pinned (stickied) notes around the English Language board first and find out what it's completely about before you dive in head-first. Get some more research done on the subject. Have you checked out the English Language Study Guide?
English Language isn't completed just because you're a Maths/ Sci student and you've done the grammar section of metalanguage. It's also done for many other reasons too. I would even dare say that it's not for the faint-hearted and perhaps an acquired taste (some say it's dry), but it's DEFINITELY not the easy route out of Mainstream English (some say it's more effort). Juggling it amongst the rest of your current 7 subjects will make it harder... and that's not going to be easy. It'll be fierce... but it's a challenge, maybe more than Mainstream English. Then again, it may be the choice you're after.
Seriously, read up on it and make your own decision, because no one knows you better than yourself.