Am I Pregnant? Help :(?

ok so the big thing is, I can't suck in anymore. I used to be able to do it really well and now I feel like ima throw up every time I try. And I've been craving and eating weird things. Like right now I'm eating pretzels and dipping them in ranch. I just looked for a sec and was thinking, what the hell am I eating? I haven't got my period either and was supposed to start today. Help? I'm 16.