I think it's pretty normal to have that sore/stretchy feeling. I'm getting it this time around as well - you'd think my belly would already be stretched enough! No idea what to help - I usually just end up rubbing it absentmindedly when it's bothering me.

And as for heartburn - I just chew on Tums, but fruit tingles also help. I think if it gets really, really bad you could ask your midwife/OB about something stronger.