I had a scan at 2 months because I thought I was three months and the cyst was 7 cm then I went for my 3 month scan and the cyst was 7.79... Is this consider to be big?
If you are not experiencing problems then this is fine. It is quite common for cysts to grow in pregnancy and this is only a very small increase. You may need another scan to check the size again as your pregnancy progresses. It may reduce in size after the birth.