Bf/ sex problems

My bf took my virgin and we have had sex like 5 times now I have came like 3/5 times and he has only came once 😕 he says that its Bc he can't cum in 20 minutes that it's not long enough that he needs 20 more minutes but I feel like it's something I'm doing wrong idk what yo do Bc I rlly like it and I feel like he doesn't even tho he says he does and also my body count is obviously 1 but his is 3 ( I'm the third) so I feel like he doesnt cum Bc I'm not as good as the other girls but I dunoo what to do