Lack of appetite in 3rd trimester

I don't know whats wrong with me, but I can't bring myself to eat lunch. I have tried eating a smaller breakfast and eating it earlier, but it doesn't help. Today I just ate 2 yogurts and a cheese stick for lunch. I eat breakfast and I eat dinner, I just want to pick or not eat anything at lunch. I started out a little heavy in pregnancy and have gained 4lbs thus far. Baby is healthy, but please tell me I'm not alone. Is my baby getting enough nutrition? How do I regain my appetite?