If I have a preexisting condition can I not get health insurance?

I have symptoms of urethral stricture that has not been diagnosed formally. I have had treatment related to it indirectly but the period will be over around 6/15/11. What I mean is I won't have had treatment, advice, etc for 6 months prior to enrolling in any health plan. Does that mean that I do not need to disclose the symptoms? I have not been formally diagnosed as that requires tests. I do have some symptoms now but am unsure about how to proceed but do need medical insurance as I may need surgery in a couple years.