You said you lose your erection when you stand but I'm assuming you mistated the problem and you lose your erection when you lay down. Otherwise, why wouldn't you be able to have sex? Even if that is a problem, there are other positions you can use where you remain upright.
Yes, you can get your wife pregnant this way. But I think you should get help for your problem if you cannot have normal sex with your wife. It can't be very satisfying for her to receive no stimulation and only get a deposit.

Thank you for your time and input, basically I need to stand to have sex because I am a 6ft 2 and 300 lbs guy and my wife is 5ft 2 and 105 lbs and I don't want to crush her with my weight (), also, she complains that my penis is too big for her and hence we opted for the deposit method. If you have further or better way to hellp us out, it is highly appreciated.