Outside of what was said above, I will add two things for you to think about:
First, don’t neglect paying attention to your pick angle, you should not hit “straight down” (or up) on the strings. You can call that perpendicular if you will. The pick angle is very important for “cutting through the strings”. Slightly angle your tip - maybe 30 degrees, and then on your down stroke your hand angle should go from “9:00 and finish at 6:00”. It’s exactly opposite on the up stroke. I know that at your level it is difficult to actually “feel” the pick just like you can the tip of your finger. That will come after years of playing, but ultimately you will get there. Be conscious of both your pick angle and stroke angle.
Second, and pertaining to learning rhythm, I’d like to think that a lot of us learned it like a drum beat. I know I really wasn’t taught how to do a stroke or the proper way. Instead I was taught to say “Boom Chick” The “boom” is the down stroke and the “chick” is down. “Boom” hits the base note or (root) and then the “chick” goes down across multiple strings to make a strum. You have to keep the beat going in your head just like a drummer. We’ve all done it…just keep repeating it in your head and in time …Boom Chick Boom Chick Boom Chick, etc
Once you get the “Boom Chick” down you then graduate to the “Boom-Chick-A” The “A” introduces one to the “upstroke” at this level. Just repeat saying if over and over in your head…and in time… and make sure your hand keeps the beat. You’ve learned the “boom chick”, now all you have to do is an upstroke and make the “A”.
You’re pretty much just banging through the strings at this point. We’ve all been there, we all learned exactly like you are. Don’t feel special… we all worked our way through it and fought it just like you. It will come over time, just keep plugging away. 30 years from now you’ll still be plugging away and trying to learn something new with your pick and it’s just as difficult. But you’ll look back and appreciate what you went through and all the effort that you put into 30 years of playing…trust me me when I say that I’ve only got maybe 30 more years of life left and there is no doubt I’ll go to my grave thinking “Man I never did get good on guitar”. It’s a lifetime passion. It’s also a hobby. If one wants to get really good, then they need make a lifestyle out of it… just like pro athletes in sports. They eat, sleep and drink their sport, they train, they practice, they study, they work on technique, etc.
I wish you the best, it’s an enjoyable journey and well worth the effort. Try saying the “boom-chick-a” in your head and you’ll find that your brain is actually focused on keeping in time than it is moving the hand and then you’ll be relaxed and make a smooth sound and not loose your pick.