What does it mean when a friend who always texted you back immediately now starts replying only by the fag end of the day or the next morning?

He's preoccupied with life.

Could be any number of things !
A lot of folk are preoccupied with their own worries at the moment.

he got pregnant obviously

Other priorities, at least for now.

He is busy!

It means he is not thinking about you the whole day, as he might used to be. He is busy with something other the whole day, and you are trying to make him think about yourself.

Whenever I do that it’s because I got bored of the person or I don’t like them anymore.

Lost interest ..