This has been my experience. I'm in a similar position to you (weight wise), but have been riding since January. I'm at about 3200 miles right now. As I've ridden and my legs, lungs and body have gotten stronger, I'm supporting more of my weight on the pedals than I used to -- and this results in less weight on my sit bones by default.

You may also want to check the tilt of your saddle. It ought to be LEVEL (use a large hard-cover book or something that can rest on top of the saddle and place a carpenter's level on top of that. Is it level?) A little tilt forward or back may be your preference, but start with dead level and work from there over time.

Also, if you're hopping on the bike, getting settled and then powering away in that same position for the entire ride, you'll want to throw in some random position changes here and there -- so blood can flow, different muscles can be used for a few seconds, etc. Imagine sitting down in your office chair and then not changing positions, crossing your legs or ANYTHING for the next X hours. You'd be in pain by the end of the day. Well, same holds true on the bike. Stand up once in a while and push a bigger gear for 20 seconds. Ride on the tops for a minute if you're not near any traffic or other reasons you might need to be hovering on the brakes... Doing this can also help with hand pain.

Great work out there and good luck!