help! period in 2 days and no signs/symptoms......

hello... so I'm 18 years old and I've been with my boyfriend all the high school. we only started having sex like last may (2016) after his birthday...I'm not on birth control because I had a rough living experience with my mom and she never wanted to help. now I live with my dad and I want to be on birth control, but I don't have insurance. so, this is probably gonna sound weird but sometimes we have sex when my period is ending.. usually it's like 2 or 3 days before my period is supposed to go away. so at my last time of the month, it was 2 days before my period was ending and we had sex... I was on top and I had to stop, so I sat up and then he's like, "I really hope you're still on your period because I just came.." & I freaked a little at first and then I'm like, yeah I'm on my period, impossible. so I brushed it off and now, I'm supposed to get my period this Sunday (the 26th) & usually the week before my period I get moderate cramps.. this usually happens every other month. so sometimes I'll have cramps and sometimes I'll be moody. this week I've been more moody and not really any cramps... so now I'm kinda worried.... can you get pregnant when you're towards the end of your period...?