What Causes Bulged Stomach Along With Irregular Periods?

hello doctor

My wife is 21 years old

her stomac automatically gets big like a pregnant lady

but becomes ordinary after some time for last 3 months

Also this month she recived the periods in 8 days gap

for last 3 months her periods came only 3 days

but this month the first period was on 8 th and the next came on 15 th