Honestly, it sounds like the bike isn't set up properly. I could definitely be wrong on this, but it seems like if it were just a saddle issue, it would be the sitbones or soft tissue that was causing pain. You shouldn't have your weight on your tailbone. It sounds like you could be too upright. Maybe you could get a longer stem. If you purchased your bike recently, maybe you can ask your lbs to do a fitting to make sure its set up properly.

Ok, I just noticed that you have a comfort bike which has a more upright position. I have zero experience with this type of bike so my comments could be completely off. I would still recommend going to your lbs though and asking for a fitting if you aren't comfortable and can't figure it out. They might be able to tell by you just biking around the parking lot a little.