A couple pieces of advice.

First, don't refer to girls and women as females when using English. While accurate, it is currently a word tainted in that context by its use among incels and assholes, so it makes it seem like you're one of those.

Second, at 19, sudden arousal from visual stimulation is fairly common. In other words, it's normal but annoying. It even happen when you're 49, though not as often lol

But the way you control yourself is the same way you control anything. You simply choose not to act on it, and wait until the problem goes away. For most guys, the erection will go away in a minute or two unless you're spending that time thinking about things that keep you erect.

Trust me, you aren't getting laid often enough just by being around girls/women to merit thinking about it the entire time. So just focus on your breathing, pay extra attention to what people are saying, and wait it out. It will go away eventually for damn near everyone. It has to because our bodies aren't designed to keep an erection we aren't using. Now, if there's enough friction in your pants, it may take longer than otherwise, but it'll go away eventually.

You are young, and that is normal.

My advice is to remind yourself that girls are people, too. If I focus on the fact that I'm talking to a person, and I ignore the fact that that person is a girl, then I find that I act more normally around them. I think the girls appreciate that, too, since if you act uncomfortable, then they will feel uncomfortable too.

It's normal. Just keep composure and don't be creepy about it.

Don't let the downvotes get you down. @southsamurai is right about not referring to women as "females." I'm hoping that's the only reason you're getting downvotes. Aside from that, it's a valid question that I don't think deserves downvotes.

Do work on learning how to take your mind off of it, though. Mindfulness practices can help. Maybe try being proactive -- don't wait until you've already got an erection to apply your remedies.

Experiment with masturbating more. Experiment with masturbating less. (I think different people are different. Some get hornier the more they masturbate. Some get hornier when they masturbate less.) See what helps you control your libido more.

Be decent to people, beautiful or not. To the best of your ability, don't make your problem their problem. But also, to the extent that you can't control it, don't beat yourself up about it.

It's actually a sign of early onset dementia.

Boners are to be celebrated! Older men pay lots of money for something that you get for free.

Try not to lose sleep over it. As @violetraven@lemmy.blahaj.zone said, don't call attention to it and you'll be fine. It's even less weird than getting a boner in the middle of your physics presentation. Here, you at least have an obvious reason for the boner.

at 19 not the way in high school but at over 50 I still have to make an effort to be looking at pretty women in the eyes.

The solution is to examine why it makes you uncomfortable. Most likely irrational thoughts are at the root of this. If it's an involuntary response of your body to external stimuli, then it's ultimately self-harming and destructive to punish yourself for what you can't help. Especially when you consider that as humans, we are animals, and animals have the same response.

If how people react to my asexuality is anything to go by, you would probably be seen as more normal than the alternative. I can't speak for other women, but if you're a courteous human being, I for one won't judge you.

Are there things about us that do it for you more than others?

I usually just think of a generic chair and it goes away.

Hold your breathe, discretly, the longer you can. Your brain will redirect blood for oxygenate the body. Then yes it's normal.

I'm 33 and it still happens.

Why exactly do you feel uncomfortable with an erection around them?

A huge amount of biological beings reproduce sexually, including humans. Women are generally sexual.

Almost everything we do as people is somehow connected to having sex. The urge to look for power evolved because it lead to better survival, and to more sex. Being cooperative/altruistic led to more sex. And so on, almost every one of our traits evolved so we can survive longer to have more sex.

But there's also sexual violence and unwanted sexual advances. Thus sexuality is also discouraged by our society. I would guess that this in some way lead to you being uncomfortable?