Please Help!!

Okay my beautiful ladies.. I (f23) was cuddling with my boyfriend of 6 months... we have never had intercourse ever just because I am not sure on how secual education works and I dont want any slip ups... so I need your advice on this one Ladies please... we were cuddling about 4 days ago... i took my underwear off and he slid it in for only about 6 to 8 seconds and thats when i immediatly said Couldnt do it... i know this may sound dumb... but i dont have anyone to go to... could this slip up cause a potential pregnancy? I've been worried...