My problem is I can’t do 1. If I could do just 1 I feel like I could slowly work my way up to 2, 5, 10, 100, whatever. Starting at 0 trying to get to 1 feels insurmountable.
I have tried all kinds of advice from the Internet. I tried doing pushups against the wall or on my knees. I kept that up for quite awhile, but still never got close to doing 1 real normal push-up correctly. I don’t have the discipline to keep going when it takes that long to get any results.
Hold yourself in the top of the push up position then as slowly as you can drop into the lower position with your chest on the floor. The slower the better. When you’re on the floor, reset and go again.
Do 10 in the morning and 10 at night for 2 weeks and I guarantee you will be able to do at least one real push up.
Maybe try doing curls with 3/5 pound weights instead! Or standing shoulder presses. Do that for a few weeks and then return to pushups. At that point you'll be strong enough to do 1. And then as you say, 1 becomes 2, 2 becomes 5, and 5 becomes 100. I couldn't do more than 15 in a row on January 1. On August 16 I did 525 in 2.5 hours (I know this because it is in my Google Sheet).
If you can do 3+ knee pushups then you should be able to just about do 1 normal pushup. Surely if you progress to 10+ knee pushups you can do at least 1-2 normal ones.
Maybe you are not eating enough protein to grow your muscles when doing the knee pushups.
This is kinda sad to hear because I think it's more-or-less an immutable fact that, barring disabilities/injuries, anyone can do pushups if they try every day for just a few weeks, and then you'd be off to the races. Actually it feels really good to have that part of your body start to "click"; a bit of a "this is right, I was built to feel strong here" feeling.
I think there's some widespread misconceptions about how "starting" an exercise is supposed to go. The problem is that starting out is nothing like doing them once you can do them. (In no sense am I an expert on this; I just have some intuition about it and have coached some friends through trying pushups when they couldn't.) There is a whole chain of muscles involved in the motion--actually, there are a bunch of different chains, because there are a bunch of different kinds of pushups that use different muscles. The thing that goes wrong is usually that there are some "weak links" in that chain: muscles you've never really used before, and maybe don't even know how to activate. The actual pushup motion, the one you see people do online or whatever, is not really possible until you have these muscles linked up. It's just not going to happen. Maybe you'll eke out one with tremendous effort, but it won't look or feel like the pushups other people do.
Instead the way to start is to do anything at all that feels doable but a bit hard in that position. Yoga positions like down and up dog are great. Staying in a plank for a bit is great. Play around with the arms in different positions. Go down just a little bit but don't stay down. Etc. If you do things like this for 5 minutes a day, just pushing yourself to find things that feel tough each time, I think you will be able to do a proper pushup in 2-3 weeks. The thing to keep in mind is that the goal is to learn how your shoulders, chest, and back work together. For example, instead of putting your elbows out wide and trying to stay up but falling--try narrow elbows and then shove the ground as if are pushing a heavy grocery cart. Or, stay on vertical arms but rock forward and back. Or, stay on your elbows, but lift your feet up on something. Whatever is hard but doable.
(This is all 100% vibes, I don't know anything about anatomy or fitness. But I'm pretty sure it works.)
(Mostly I have coached people on the mindset about starting exercises with regard to climbing and particularly pullups. New climbers tend to not understand that there is just no way they're going to do a whole pullup if they can't do the first quarter second of the pullup, which is the hardest part, due to the awkward angle of your arm and shoulder giving a mechanical advantage particularly when you don't have much lats/scapular muscle. So train that first! They tend to cheat that part instead of working on it and don't understand why they're not making progress.)
> anyone can do pushups if they try every day for just a few weeks
No, they can't, not even close. Fatties need to lose weight first or start with bench presses. It might not even be the matter of strength, the belly is literally in the way.
And if you're a "fatty", play to your strength - the very strong legs you have built up carrying extra weight every day.
If you do leg cardio (walking/treadmill/cycling, etc.) your leg muscle will likely never go away and you can use it to burn off as much fat as you wish. And once that is going on you can add other non-leg exercises.
I have tried all kinds of advice from the Internet. I tried doing pushups against the wall or on my knees. I kept that up for quite awhile, but still never got close to doing 1 real normal push-up correctly. I don’t have the discipline to keep going when it takes that long to get any results.