My Kryptonite with the Sicilian..

The move c4 when I'm playing the sicilian is so annoying and hard to deal with. 1.e4 c5 2. nf3 d6 3. d4 cxd4 4.Nxd4 Nf6 5. Nc3 a6 6. Be2 e5 7. Nb3 Be7 8. Be3 Be6 9. Na4?! Nbd7 10. c4 Rc8 and I was scared to take on e4 for some reason even though I shouldn't have been, but still in this position I'm given the evaluation of being somewhat better, yet the recommended move for me after white's next move, 11. Nd2 is 11..b5! B5????? Why? Would any of you play this, or find it? Its apparantly by far the best move in the position and if i don't play it, its equal again. Is this a common idea when white has c4 in the najdorf in this variation? Otherwise I don't know how to deal with this system, its so annoying and I can hardly move without weakening my position. I ended up losing this game after getting impatient and lashing out with f5 a few moves later but his position was already slightly better because of all his space. Any suggestions? If any sicilian players out there ever had such a problem.

And b5 stayed the number one option for me to play for the next 3 moves before I played Nb6 putting myself in a worse position and not allowing me to play b5 probably ever.

Hmm..