Energy levels

Almost 19weeks and still have no energy. I can't even stand and sing at church for the 15 minutes without feeling out of breath and fatigued.  One day I have energy I try to get stuff done the next day or two I have to spend recouping. Anyone else experience this.  I'm 32 with 14 yr old and 8 yr old girls this is my 4th pregnancy.  What do you do to help have energy.   and not be exhausted all the time.