Bowel problem

It has been nearly a month since I've started her with solid food, and a couple of weeks earlier was going normal and nothing seems to be a problem with her passing motion and all. Though since monday, she has been experiencing some problem during her daily bowel movement, she was making noises and making those constipated faces, and when I did check her nappy, her stool was kinda hard, not very hard, but clay kind of hard. She was crying after cleaned her and changed her nappy.

I did gave her an apple pureed on Sunday, and she didn't like it, so I stopped giving her by the third attempted. So it can't be the apple pureed, as today she still having trouble when passing motion this afternoon. Hmm...I did some research on the net and found this:

"Most of us recommend that, when you start feeding your baby, you start with cereal. The three cereals we suggest are rice, barley, and oat; all three are easily digested by most babies. Rice cereal is the traditional first food for babies: it is more digestible and less allergenic than other cereals. However, rice is also the most constipating of grains. I occasionally suggest starting with barley or oat cereals; I usually suggest that a baby be fed all three cereals within 3 weeks of starting cereals."

I am so worried now, cause not only she just showing this constipation after 3 weeks consuming the rice cereal, she seems to loose her appetite too. Although, she still being breastfed every 2 hours during day time, but I don't think that's enough after 3 weeks supplemented with a bowl of cereal. Today, she only took 4 small spoon of rice cereal, she started to be irritated and losing interest in her food. I hope it's just one of those period where she is growing and will apparently goes away tomorrow.