confuse!! need help

ok,Ive Been Dateing this girl for a couple months now and in the beginning we both expressed that though we both want a serious relationship in the future but we are not actively pressing that too hard right now. After about three weeks of talking and spending time with one another i realized that i like her more than i had planned. She has told me the same thing and constantly says that she is not committed to me yet. we havent gone a day without talking or at least texting all day,until the last couple days. she says she is hanging out with a friend but hasnt called or returned a text for the past 16 hours( i only texted twice). is she with another guy or am i just paranoid? and how do i go about letting her know how i feel about this without sounding jealous or smothering?