Although my periods are irregular meaning I probably will not come on my period in three months but it varies from time to time some times I come on for three months straight then I miss three months straight does this mean I cannot get pregnant.

Not necessarily, but it may mean you might have a harder time becoming pregnant. Check with your doctor about ways to help regulate your cycles. They can also check to see if you are indeed ovulating, which is necessary to become pregnant, and whether there is any hormonal problems that need to be addressed.