Corpus luteum cyst...anyone heard of this

Megan • 24, have a 6 year old girl and an amazing boyfriend! Expecting #2 November of 2015!!
I had my first ultrasound two week ago and I told my dr I had a lot of pain on my left side and he said I had a cyst, and it was normal...but I had never heard of it before and it's still painful and sends shooting pains sometimes. I have another appt tomarrow and I hope he checks it Bc I'm nervous it is growing!