Why am I losing water pressure inside only?  On a shallow well, pump is fairly new.
	
	
		Hi!  I have a shallow well.  We are in a drought.  Water pressure is low throughout the house and falling, despite conserving water.  I thought the problem was drought-related.  But yesterday, I broke my self-imposed water restrictions and used the outside hose to water my thirsty shrubs.  I was surprised to find that the pressure outside is just fine!  What might be going on here?
Note: Pressure has been low for two weeks.  A few days ago, I could hear a small amount of air sputtering into the toilet tank.
Also...  about one minute into a shower, pressure increases Every time  like clockwork, then fails after about 30 seconds.  The pipes "sing" during the increase in pressure.  
Thank you for your time.