I'm terrified, help?

No one on the internet is going to be able to tell you if you're pregnant - but chances are you're not.  While it's possible (you can certainly get pregnant even if your boyfriend did pull out before coming, because there's always some leakage prior to that event), it's not likely. 

You can't test with an OTC pregnancy test until you've actually missed a period.  Since you're irregular, I'd wait until the second Sunday you think you might start your period, give it a day or two, and then test.  Any test before that is likely going to be inconclusive.  If you don't get your period, and you're still unsure, the best way is to have a doctor do a blood test.  If you don't want to go to your regular doctor, try calling the Planned Parenthood in your area - they'll help you out with that.  (They are NOT just for abortions!)

Obligatory mom-speak now: please use this as a life lesson and USE PROTECTION FROM NOW ON.  Whether it's condoms or the pill or whatever, NEVER have unprotected sex again.  A baby is the least offensive result of unprotected sex. 

If you are pregnant, you've got options.  Abortion doesn't have to be one of them.  Adoption IS.  (I'm an adoptive mother, I'm happy to talk about my experience on that end of it.)  Open adoptions are becoming the norm; making an adoption plan for your child doesn't have to mean you lose contact with him or her.  You're the birthmom, it's ultimately YOUR choice what happens to your child. 

Talk to your mom.  Yeah, she's going to be mad/angry/sad/whatever.  But she might also surprise you, if you go to her and tell her you KNOW you messed up, and you're asking for her help/advice.  Your mom loves you, but I suspect she's been half expecting this conversation since the day you first noticed boys existed. 

It'll be okay, whatever happens.  Good luck.