How does one feel in the first trimester?

How does one feel in the first trimester? I wanted to just sleep during my first pregnancy, but now I'm already exhausted from morning... like I plowed the earth... constipation, nausea if I don't eat, and heartburn if I do eat... what should I do??? The belly pulls sometimes. I'll go for an ultrasound at 8 weeks, will it be visible on the ultrasound already?? From the first time I went only at 11 weeks.