Exhaustion has set in!

Well I am about 6 weeks in, or in my seventh week and I am so tired!! I haven't done anything strenuous but I feel like I could sleep all day and all night and still be tired when I get up! Plus I get lightheaded at the drop of a hat... I guess I need to drink more water. Anyway, I felt pretty good until about 2 days ago when my energy dropped off suddenly! I have my first prenatal doctor's appointment on Thursday, I'm not sure what they are going to do other than medical history, but I've heard that you can see the heartbeat on Ultrasound by this time. That would be cool :) According to the online due date calculator on babycenter.com, I am due August 26, 2005!