Can't keep erection while standing

HI guys!

I don’t know if this is all up in my head. But I just can’t get/keep/maintain an erection
While standing or on my knees - that really screws with my head since I love to try
The doggy style position or even sex while standing(which is great for public sex, what I’ve heard)
I’ve only had sex 3-4times with my current gf - we are in a long distance relationship atm.
I get morning woods and I can masturbate successfully while sitting or lying down.
I even tried to put some porn on while trying to masturbate while standing- but it just doesn’t do it for me - why!?
I tried one of my buddies Viagra - which help maintain my erection while standing - but It just didn’t do it for me
So it took FOREVER to cum.. But while sitting - everything is awesome..

I recently started PE - I get firmer erections and it seems my penis has grown a tiny bit. Is my penis exhausted?

I masturbate once everyday.. Could that be the problem?

My penis has a n-curve(which means is curves a bit downwards) plus slightly to the left.. Anything here?

I hope you guys can me help me out, it’s quite a pain in the ass :S

Oh an I’m 20 years old - goes to the gym 3x a week
And I try to stay on the healthy side of foods.
I don’t smoke or take any medication..

Regards,
Me

At the moment, not atm please :)

I don’t think you have any negative PI’s as you get well morning wood and firmer erections. Masturbation once a day should have no effect on your erection unless you masturbate and then try having sex right after.

Try some kegels. They will help maintain your erection.

Have you tried to get/maintain an erection while standing when you were with your girlfriend?

Because in my case, I can’t get/maintain an erection while standing when I masturbate, but if I’m having sex it’s not a problem anymore.
I was worried about this too, but I have done it a lot of times while standing or ‘on my knees’, so I don’t feel bad about it.