sex advice

So when I have sex with my boyfriend, I want to, I’m ready to, and i’m turned on. So we start & it’s good but after maybe 10 mi it starts to hurt. And this is an every time occurrence. We’ve been dating for 5 months and so we’ve had sex many times. Every time it hurts though, we stop. I don’t understand why or what to do to fix this problem. I’ve had a uti before and I know the feeling, it’s not like this.