If you masterbate frequently, cut that out.
I’ve read that HCG can help with volume but I have no experience with it and it comes with its own issues.
Besides that, get a lube product from A & E called Fuck Water. It’s a lube that looks just like semen. Put a big glob of that in your hand and when you reach climax, throw it in her face.
Edit to add…I know that sounds funny, but I’m really not trying to be a comedian. If your wife enjoys that, and you can’t provide it at this time, there are ways to simulate is all I’m trying to say. Don’t be deceitful about it. Let it be y’alls little kinky secret. If she enjoys the sensation, why not? If you had an issue getting hard and she was about to jump out of her skin to have an orgasm, would you tell her “not tonight” or would you grab a dildo (or some great fingering techniques) and go down on her until she exploded? I’m just saying… It’s not like you can control that kind of thing when it happens, but we can go the extra mile to make sure that the Mrs gets what’s she needs from us right?