Members of this board recommend spending 8 weeks vegging a plant that was started from seed. The main problem with longer vegetation is that the plant keeps growing tall. Typically it will double or more in height during flowering.
You did not mention what your light cycle is, that is to say how often in one day are the lights on. You need to have 12hrs of uniterrupted darkness every day through flowering. If you are not doing this than your plant is likely still just growing in a vegetative state. You don't need to rush into flowering, you can wait for the HPS bulb to come in.

Does this make sense to you?

Cheers!