Generally guys at this immature stage getting first ejaculation and it put a very negative impact on marriage life.
Anyway in your case if he ejaculate within a few minutes or just pushing the head, try to get him ejaculate by blow job and don't allow his sperm to come out fully. Give a little warm tea or coffee. Again suck his cuck, it will get erect within few minutes and he can give best fuck to multiple orgasms. Both of you enjoy with full satisfaction.
I think it is the best way to get the best from such immature guys
