how long in vegging?

It's my first grow and I have my plants under 18/18 of cfl. It's for about 3 weeks now.

How long will should I keep doing this? When will they start flowering?

Start flowering when the plant is about half to a third of the size your plant can get in your space, in flowering it will really grow

There are 2 features that distinguish mature veggie plants from immature ones. They are alternating nodal arrangement and leaves with 5 or more blades. You can flower before those features are present, but the plants will perform a whole lot better if you wait. Most strains except for equ. sats have these by 12" or so.
Peace

I started flowering my plant at 3 weeks, 7 inches tall, but pretty ushy

Really you cn flower when ever you want longer you veg more bud you get bu y are you doing 18/18 shouldnt you do like 18/6 or 20/4

yea dont 18/18 for veg stage ... if i were you i would put on 20 / 4 at least some people tend to use 24 hours light one till about 3 weeks until your prime budding time, then take off 24 hour light and work it down to like 18 / 6 for couple weeks then when you want to flower have the lights set to a consistent 12 / 12 hour light cycle.. make sure no light or disturbance occurs when lights are out..

right on dude

Dude when you veg do it 24 hours a day untill u r ready to flower. Then go straight to 13/11 for 1 week . You should see signs of gender by then. The last 4 weeks of flower 12/12. This way your nodes will be close together before flowering. And bigger buddage.