Morning sickness that lasts ALL day

Why is it that some first trimesters are "worse" than others? I am 9 weeks preg right now and suffering through some of the worst morning sickness ever! My OB put me on Zofran to help ease the "ickiness." But it is no miracle cure! I have found eating every 1.5 - 2 hours seems to help. Not big meals... just small snacks... like triscuits, rice cakes, cheese, chips, ice cream pops (you get the idea.) Also try not to drink liquid with your meals. That can sometimes make you feel sicker. Once you have found a food that helps.... STICK WITH IT! Right now I am all about frozen waffles. yummmmm! Some ladies also find sucking on hard sour candy helps. Like Lemon drops or sour skittles.