Although you've still got some time before your belly reaches truly uncomfortable proportions, all the activity going on in your body is bound to have some significant side effects on you physically. For example, your stomach is being compressed thanks to your growing uterus, so it's not unusual to experience heartburn as a result. Also, your ever-expanding midsection is likely messing with your posture, with the end result of mild to serious backaches.
Your skin is also under substantial duress, thanks to the hormones and necessary stretching. This can cause a litany of superficial changes, like stretch marks, itchiness (particularly in the abdomen or breasts, where you're growing the most) and darkening skin pigmentation. You might also develop the linea negra, which is Latin for "dark line." It's just that -- a dark line that extends from your belly button to your pubic area. Don't worry; it goes away.
Consult your obstetrician if you're feeling any sort of significant discomfort, and he or she will provide a handy list of pregnancy-safe medications that'll take the edge off.