Bloating in First Trimester

I'm nearly 4 weeks pregnant and have been feeling extremely bloated over the last few days. At first, I didn't realize what was causing the discomfort, but I later figured out that my tight-fitting panties were making it worse. I can't tolerate anything tight around my waist now. Eating anything seems to make the bloating worse, although drinking water helps somewhat, even if it makes me feel fuller. Has anyone else experienced this? How long can I expect this to last?