Chances of becoming pregnant

First off I’m posting in this group because I feel as if people in this group would know best. So my app glitched and told me yesterday I was on cycle day 5 and my partner wanted to finish inside of me and asked me what day I was on, I told him day 5 because I actually believed it was day 5, I’ve been on vacation for an entire week now and still have a day left so my period hasn’t been on my mind I didn’t pay attention to it or anything like that. My cycles are 26-28 days on average with it mainly being 26 days the most, today is cycle day 8, Would his sperm still be around when I ovulate? I know it says sperm can last up to 5days in a woman’s body but what’s the actual % to that I assume it’s low and near bout impossible. I just feel bad like I lied to him but I genuinely didn’t know and don’t know if I should tell him or ignore it.