Annulment through Fraud?

Hi there,
I have recently discovered that my husband of 3 years (together 8.5) has 2 (18 and 10) sons from 2 extra-marital affairs in his first 20 year marriage which were undisclosed to me. Should I have had this information available when deciding on a long term relationship with him, i would not have embarked. Likewise so for marriage. I feel cheated out of my last 8 years by living with a stranger. Does anyone feel that this could be grounds for annulment rather than divorce? I have paid 3/4 of the household expenses throughout this relationship and have bank details which will show this. Through divorce obviously he would be finally looked after despite vitually no contributions to a fraudulent marriage. And ultimately taking from my own 2 adult children in the long run....
Any advice much appreciated.