Ugh...I know how you feel. I switched last year to a lower dose pill and was miserable for several months. I had taken Ortho-Novum 777 for about 14 years with no problems. I switched to Loestrin Fe because it has a lower dose of estrogen and is mono-phasic (as opposed to the tri-phasic pill). It took my body a good 4-6 months to convert totally over to a new pill.
I expected *some* transition time, but after 3 months of mood swings, PMS and strange cycles, I went back to the doc and BEGGED to be put back on my old pill. He told me to wait it out, that I should start to feel better soon, my body was just so used to the old hormone levels. He promised me that if, in a month, I didn't feel at least a little better he would switch me back right away. I saw him monthly for the next 3 months until I felt "normal".
I am *SO* glad he made me wait. My body has totally normalized and I really like the lower dose pills. I have no PMS, no bloating, no anything!
After only 7 days your body is trying to adjust. It is going to take time. You can always call your doc and go in to talk to him/her if you are concerned. But my guess is that it is just normal hormonal adjustment.