From your description, it appears you have a gap between two
portions of the abdominal muscle called the Rectus muscle.
What is happening is, you have developed a condition called
"Divarication Recti " which is a kind of hernia
that gets aggravated
with any activitivity that increses intra abdominal pressure, like
heavy coughing, sneezing
or lifting weights, or build up of
intestinal gas. An abdominal binder (Velcro) will be helpful when
you do any excercises such as weight lifting or push ups.
In some cases , if the bulging from internal organs get stuck ,
that could create a problem and that is an indication for surgery.
They can do a mesh repair.
Sexual activity, again can make the hernia worse . But the abdominal
binder should help.
Hope this helps.
I wish you well.