Too young too be pregnant...i just need some advice! please

Hey there. So my boyfriend and I had sex without a condom during my period about a month ago. He pulled out of course. So that frightened me quite a bit. Then about a week and a half later we got carried away and did that again but stopped A LOT sooner. yet right after i pulled away...literally like 10 seconds later he came. Ive been scared ever since. Ive never really been one to keep track of my period..like when i got it and when itll come next.(weird i know...and i know i definitely should be anyway!) but yeahh so im totally estimating on when i should be getting my next period. It shouldnt come any later than 2 days from now(Jan. 6th). And i think even that may be pushing it. but again im not entirely sure. Ive had just some sliight symptoms of pregnancy though. Like slightly sore breasts..(which i do get before my period) and now this light cramping in my lower abdomen which i have had for about 4 days now? on and off kinda but nothing too painful. sometimes i wonder if im just being paranoid too though. Yet the cramping usually doesnt happen before my period though. im extremely afraid because i am only 17! how strong is the possibility that i could be pregnant? is there still a chance im not at all?! ive been really freaking out the past 4 or 5 days ow and i know that doesnt help...but im scared!