Pregnancy affects every woman differently, because of genetics, age, health, even personal outlook. And even for the same women, each pregnancy can be different.
Not every pregnancy involves morning sickness -- which is a misleading name for it, as it can occur throughout the day. Some folks get it really bad early on, and are lucky if it lets up in the second trimester. (According to my reference book, What to Expect When You're Expecting, it affects just over half of all women.)
I'm 35 weeks into my first pregancy, and I haven't had ANY of the "typical" pregnancy woes. No morning sickness, no cravings, no sciatica, no hemorrhoids, no back pains, no swollen feet, no varicose veins, no gestational diabetes, no stretch marks. Boring and easy, but I'm definitely not complaining. I'm counting my blessings.
If you're not having morning sickness, consider yourself lucky. (And don't brag too much -- many suffering women will resent your good fortune.)