If you followed your CDC's advice and cut down on the carbs before you started then it's possible to go into ketosis within a couple of days.
More commonly, it takes four days or so. By all means, use a stick to test. If it doesn't change colour at all and is still 'beige' then it's negative. Any shade of pink shows you're in ketosis.
Best time to check is first thing in the morning when your urine is most concentrated. Any shade of pink is a positive ... you're either 'in' ketosis or you're not. The only difference is that if you get a dark pink reading during the day
, you're not drinking enough as the ketones are concentrated. If this happens, glug more water.
You might find it useful to buy your own ketostix (get them from any local chemist or online - don't bother with Boots ... they can get awkward). They cost about £5 for a pack that lasts ages.
Once you're in ketosis, provided you don't 'cheat' then you'll quite happily stay there and don't need to constantly check.
Hope this helps