Here’s my best advice if you’re finding it difficult to sing while you play guitar
It’s really common for beginners to find it difficult at first to accompany themselves on guitar while they sing a song.
The reason is normally because they have not made the guitar side of things automatic and second-nature. This means that they are having to devote too larger percentage of ‘brain-power’ to chords and strumming which leaves little in reserve for singing, remembering lyrics and the emotional delivery of the song itself.
Once your playing becomes more ingrained and second-nature you’ll find that you’ll be able to pretty much forget about it while you sing a song. It’s something which will take care of itself.
In the meantime I would suggest that you STOP trying to perform a full strum on your chords and just do a single down strum on each new chord.
Sing the melody line over the chord as it sustains and then go to the next chord.
This creates a kind of intermediate stepping-stone where you are accompanying yourself on guitar while singing the song but because we’ve reduced the amount you have to do on guitar you’re left with the necessary mental resources to actually sing through the song.
You should continue to do this until your guitar playing has developed enough to where it can function in an automatic way.
Anytime you have trouble with something musically or on guitar, try to look for these ‘stepping-stone’ solutions. They will create a ladder which is easier to climb and allow you to continue making some kind of progress.
This is one of the keys to making your rate of improvement as quick as possible.