I shot very low the whole time, only managing to hit the center of the target 3-4 times. I'm not sure why.
This is extremely common for new shooters.
The human reflex system is designed to protect the face and head, especially the eyes. Something jumping around in front of the face, making very loud noises and bright flashes, throwing empty cases around, activates that reflexive protection system and results in the shooter anticipating recoil. The most common example of recoil anticipation is a trigger yank which pulls the shot low.
Some folks recommend dryfiring to help get your reflex system used to the idea of pulling a trigger without the muzzle blast/flash and recoil. It can help you train yourself to focus on the basics and to help ignore the distractions. Just be careful about dryfiring. Here's an excellent resource on safe dryfire practice.
You should make sure that you have good quality hearing protection that fits you properly. Your comments about being overwhelmed by the noise suggests that you might want to double-up on hearing protection by using foam earplugs along with muffs. Also be sure that your muffs fit properly. When they are on properly and fit well, pushing on the muffs should produce a distinct sensation of pressure on your eardrums. Since your reflex system reacts to loud noises, cutting down on how much noise you have to deal with will probably help.
Some people find that concentrating on watching the front sight during recoil, or watching it as it comes back down from recoil onto the target, or watching for the muzzle flash can help with recoil anticipation. Basically it turns recoil into something you want to observe rather than something that is alarming.
For the rest, just concentrate on the basics. You'll want to take a good stance, control your breathing, take a proper grip on the pistol, align the sights correctly, squeeze the trigger straight back instead of yanking and then follow through after the shot. None of that is complicated or difficult, and part of it is building a routine that helps you be consistent.
Here's a good video showing how to properly grip a pistol.
There are many resources on learning to shoot on the internet, but it sounds like you could benefit from some professional training to get you started properly. I'm not talking about a multi-day tactical class--just an instructor who could spend an hour or so with you to get the basics ironed out. It will help you avoid creating bad habits and will get you started on the right track.