Try to relax a little bit.
If you were getting undressed and your bf was just putting his penis within your vaginal lips without pre cum or ejaculation.....then need not to be worried as in this pregnancy
chance is nil.
And if any fluid comes out from his penis...then there is chance of pregnancy 20 to 25 per 100 women year.
So it is better to wait for next period and if it is missed,do a urine test after 7 days.
If positive,consult with your gynaecologist.
All the best.