Short sex...

My boyfriend and I have sex all the time. But the problem is that he cums SO fast. Like the longest time we had sex might have been 5-7 minutes. Obviously it feels amazing and I love having sex and getting intimate with him, but I want to keep going! But when he's finished, he's tired and he is to sensitive/numb to keep going. How can I make him last longer. I just feel like it's not fair he can finish but I can't cause our sex time span is short. Please fucking help me.