So i think i may be pregnant... but my boyfriend always said he would punch my tummy if he "knocked me up"?

I am on the pill and i haven't missed any..we usually use condoms and he just cums inside of me since he has one.. but we've done it a few times without one and he accidentally cummed in me a couple weeks ago. I know its probably my imagination or something but my tummy has been feeling funny like i have butterflies every morning and evening. And i feel like i have a constant headache.. also i bled a little bit about a week after... im not sure if any of this means anything but im kinda starting to worry and i don't get my period for another week or so... Im 15 and so is my boyfriend.. he always jokes about if i get pregnant hes knows i won't abort so he'll just punch my tummy.....So im too scared to even mention this to him... HELP PLEASE