Agreed with the other members. You will need to practice the rhythm until it comes to you naturally (which it will, don't worry).

I recommend practicing by playing the guitar and trying to have a conversation. It may sound silly but it has worked for people!

A lot of people have trouble singing and playing because they are still watching their hands when playing to make sure they hit the right chords. Again, don't worry you will get it with practice.

When learning to type on a keyboard at first you watch your fingers to make sure you type the right keys. Eventually you can type and read the computer screen at the same time.

This applies to physical memory. Your hands/fingers eventually just know what to do and where to go to achieve the desired results. It takes practice and dedication, but you can do it!