Period has been about 8 years now, had sex with boy once, used condom 100% of the time, ejaculated outside a little after. chances of being pregnant?

Very slim: As long as not ejaculating on you / near vagina, then sounds like "safe sex" and should have minute risk of pregnancy. If concerned, can take home pregnancy test to confirm.

PREGNANCY?: Condoms are not100 percent safe but if your period is not late, chances are you are not pregnant.

Near zero but...: There is very little likelihood that you're pregnant. It would require a failure of the condom in most cases. Ejaculation outside almost never leads to a pregnancy although never say never. Certainly check a home pregnancy test and reassess if it's negative. If you still don't have your period check again in a couple weeks. Have a great day and keep using condom. Great work!