My only advice is to just keep at it. Chord changes will come... for the ones you are having trouble with, just review the video for that particular one, and go slow. A zillion times slow if you need to. Then work it into whatever song you're playing. I found playing 3 chord songs helped me a lot. Then I gained more confidence and tried more. Practicing chord changes on their own for a long time got really boring for me so I had to start learning some songs. It was after that that I really started progressing. So once I could actually apply the chord change, it clicked in my brain. And muscle memory is an amazing thing.
I played nothing but melodies for the first couple months and it was hard to get into strumming and chord changes...but now I'm really pleased with where I'm at 5 months in. Strumming full songs, exploring Blues and Acoustics (peaking at those lessons!), recording myself playing and documenting my progress, and continuing my Fundamentals courses. I'm halfway through Fundamentals 2 and will likely be working on scales for awhile. But I'm really anxious to get more into Acoustics which I've already dabbled in.
It's really good you're taking your time. Sometimes I fly through things too fast the first time because I'm so excited to get to it. But then I have to go back and really take my time studying it. Your focus and concentration should improve with the play alongs, too.
Isn't this journey fun though?!
“Often, what seems like an impossible climb is just a staircase without the steps drawn in.” Robert Brault, American Operatic Tenor