Is it bad that i am not eating a lot?

I am 18 weeks pregnant and my appetite has noticeably depleted. When i was around 10 weeks i has the most monstrous appetite in the world. like i was literally eating every food i could see in sight. But now i don't feel the urge to eat as much. is this bad for the baby? Also I havnt gained a lot of weight. Since i found out i was pregnant i have only gained about 3 lbs. Im jus worried that this is bad for the baby. is it?