Im 17! am i pregnant? hard breasts, stabbing pains in belly, dizziness!?

I've got stabbing pains in my belly and I'm really tired all the time. I'm also dizzy a lot and my appetite is really small one day and massive a few days later. All the foods I used to love make me feel sick and smells revolting. I haven't bled for 4 weeks and I'm really bloated! I just feel completely different and ill quite a lot of the time. My boobs have increased in size and have gone really hard. What's going on? Am I pregnant? Or is it something else??!!