sounds like your putting more than enough away mate, but better that than not enough. if your new to windows in past year, you've done really well, it takes time to get the right mindset and technique up.
I drive a couple of days a week, it sounds like you were on very good money trucking, don't forget your prob working a lot less hours now, on 3am starts, breaking the law for your boss, working your backside off for somebody else's benefit. don't forget your 'profit' always looks worse due to expenses, expenses which you wouldn't be able to claim as a PAYE. stick with it mate, as said fact your in profit in first year is big thing in business these days. this year sure you will start to see the benefits.
oh, and as been mentioned, try to get tax return in early (get a good accountant if not got one already,) so you know where stand with payment on account. might have nice windfall there. and accountant can project next year's figures so you won't get caught out.