My girlfriend probably doesn't love me anymore..?

I've been with her for about 8 months now and the first perhaps 5 months were absolutely amazing, but then I started getting the feeling that she lost interest a little bit. I love her almost too much, but I'm not sure if she still loves me (I know she loved me a few months ago, there was no question about it). I got nervous, so I went on her facebook and found out that she wrote to one of her friends 2 months ago, that she is in love with an old teacher of hers (who is 36, she is 19, I'm 18). She told her friend that she loved me but that it sort of started to disappear after a few months, but she is still happy with me and knows that she couldn't be with the teacher, so she didn't do anything so she doesn't lose me as well. She also said that she would probably forget about the teacher after a while..

After I read this, I'm quite broken, I don't know what to do. It was 2 months ago and it seems fine now, only thing is that she doesn't show that much affection (I always start kisses and say I love you and she just says I love you too), but she has always been a bit shy and didn't use to do that before much either.

What should I do? Should I ask her about it, or should I leave it for now..?

I am really really in love with her, maybe it is so strong because it is my first serious relationship, but she had a boyfriend before me for 3 years and I don't think she is into the relationship as much as me..