Nothing wrong with being a bit keen

I'd recommend picking up James Stewart's Calculus: Early transcendentals and working your way through the basics to get a firm grasp of calculus, definitely devote a lot of time to sequences and series and understanding the principles underpinning basic calculus. That is, if you're keen on Maths.
As for Biology, Chemistry and Physics, working your way through Khan Academy videos is a good place to start. The courses are mainly geared to AP students but most of the content is relevant to a first year uni course. I am a big fan of Patrick JMT, but as for Maths and the fundamentals, I don't think you can go wrong with Stewart.
And if you're super, super keen, pick up Spivak's Calculus texts, those things are amazing.