So embarrassing, but this happens to me just about every time we have sex, just as Mom2Many's link says. Over the years I've learned how to have other types of orgasms during sex, but sometimes I just need to "gush."
My guess would be female ejaculation, but isn't it possible for your OB to determine whether or not this is amniotic fluid, just to be safe?
ETA - After reading other responses, I'm really starting to feel like the freak of the group.
I think you have to listen to your OB and trust him/her to help you determine whether or not this is your water breaking. However ...
Everything you described sounds exactly like female ejaculation to me. The consistency is just like water (not slipper or thick and creamy or anything else, just plain water), and there is no smell. It can be a little or a lot (wet sheets, wet mattress, etc).
If you weren't 36 weeks pregnant, I would tell you this was female ejaculation without a doubt. Since you are pregnant, better safe than sorry.
Good luck with the rest of the pregnancy!!!