I have a bulge on my lower abdomen. what could it be? it doesn't hurt i notice it when i lay on my back.

Hernia : A soft bulging mass in the lower abdomen as described in this question is most likely due to a hernia. This is commonly caused by a congenital defect or weakness in the natural seams of the abdominal muscles. Abdominal obesity is a major contributing factor and weight loss may help prevent progression. These can occasionally become complicated if become strangulated.

Diastasts?: It could be a separation of the muscles that sometimes happens due to the stretch from pregnancy and is harmless. It is usually an up and down bulge like from head to toe. Then, on the other hand it could be a small hernia. It might do you well to have it checked because if it is a hernia sometimes( not always) they will fix them when small cause it is so easy. Not always do they enlarge