I have an escape 3 ... 5'10 and 214 pounds i used to face the same problem as you did. Here are the few things i did to almost get rid of it keeping the seat that came with the bike (keep in mind i ride it more for the exercise as there isn't anything worth looking in the concrete jungle where i live):

1. Try adjusting the seat angle and be conscious of your positioning on the seat, now i know its a small seat but still .
2. Always make a habit of getting up and carrying your weight on your feet and pedals instead of saddle when you are cruising (not pedaling) - this helps me a lot.
3. Above two have worked for smaller rides with moderate 300 ft. climb and drop. I would suggest you get a saddle if you plan on riding 30 miles or more on rides.

Now after riding escape 3 i would say the pedals more than the seat need an upgrade cause they are flimsy and cheap.