I don't know if the rules are different for self-employment, but I was under the impression that insurance companies are now required by federal law to cover all pre-existing conditions.  But your coverage has to be continuous, meaning the new insurance has to take effect the day after the old policy is no longer in effect.  If any time is allowed to lapse between the two policies, you can then be denied coverage because the condition would (technically) no longer be considered "pre-existing," but "new."

The word "waiver" in the papers your insurance company wants you to sign makes me nervous.  Usually when you "waive" something, you are giving it up.  In this case, it almost sounds like you are being asked to give up what is yours by law, which is coverage for pre-existing conditions.  I would read the fine print very, very carefully. 

Shortly after my son was diagnosed with CAH, my husband almost took another job, so I looked into this issue pretty thoroughly at that time.  We have Empire (NY) BC/BS now.  At the time, I also looked into BC/BS of Michigan, as well as a number of different HMO type policies, and pretty much came up with the same information, no matter who I asked.