my bf can't cum through sex but we are trying help

My boyfriend  can't cum through sex so he is finishing himself off then puting it inside me we are trying for a baby this is so hard he has always had this problem dunno what to do I've surrgested we just turkey based but it's awkward as hell and he's sure it will work this way nightmare I don't want to upset him but i don't see how the sperm can go up this way ?? Help any ideas please xxx this is the man of my dreams I love him so much . He's the love of my life I can't tell you how happy he makes me xxx