[Sleepless]

I'm 16-years-old and my boyfriend is 19. We've been dating for less than a month and have had unprotected sex 4-5 times already. I've been having some troubling sicknesses lately, and I'm looking to ease my mind because possibly being pregnant is all I've been thinking about lately and it's worrying me.
Here is the situation:
I am not on birth control, and we didn't use a condom. The first time we had sex was only the 4th of this month, and we did the "pull-out method". With-in the next few weeks and up until now, I've been sick as all hell. Nauseous in the morning and at night. More moody than I have ever been - yelling at my boyfriend all the time and crying at the smallest thing that upsets me, not to mention this anger I feel all the time now. Sleeping all the time - at night, through school and when I get home from school. I used to be able to go 2 days without a meal but now I eat all 3 a day or else I feel sick. I have to run to the bathroom to pee all the time even when I don't drink anything. I had cramps about a week after we had sex and I thought I was getting an early period - they lasted a few days, but no period...
I am expecting my next period within a few days, and so far - hasn't come yet.
I should probably wait until I officially miss it to freak out, but I can't help it. My boyfriend brought it up wondering if I was pregnant and ever since, that's all I can worry about. Like, My boyfriend was crying on the phone with me saying how he's not ready for a kid (he works at Burger King and lives with his parents).

I'm trying not to freak out because in reality - it could be nothing, right? I could just be sick lately.
But I guess what I'm wondering is, what are the chances? I mean he did pull out. But is there a big chance of getting pregnant from pre-cum?
I don't know what to think =/