Can't cum with my boyfriend?

So idk what my deal is but I've never been able to cum when I'm with someone else. I've only came once with my boyfriend and it was because I was doing it and it took like 30 mins.. but when I'm by myself it takes me less than 10. It's always been this way... I don't understand why? And it makes him feel like hes not doing a good job when thats not true :( Any ladies the same way?