Girlfriend trouble, please suggest what is wrong.?

Ok. so shes a very nice, and respectful girl. she left me for her ex that she was doing a "long-distance" relationship with that she told me just wasnt working out. and up until about a week or two ago, she loved my sweet talking, and would say so, but these 2 weeks she hasnt been saying much about it, and she hasnt been texting half as often, and when i ask her if anything is wrong she always says no. how am i supposed to know shes not doing to me what she did to her ex, or shes not getting tired of me, or if she just wants a little space? if she wont answer me.