Answer: This is a serious issue. When you receive SSI benefits, you are required to report any changes in your financial situation. Ideally, you want to report these changes within ten days of them occurring.
SSI recipients are periodically called in to talk with local office staff to see if they are still eligible. If you have not reported your marriage, at that time, they will catch it. You will likely then receive a significant bill (an overpayment) from the SSA for the money that you should not have been paid.
If you actively try to conceal the fact that you are married, you could face criminal prosecution and potential jail time.
All that said, once you have reported your marriage, it is possible that you might continue to receive benefits. It is not being married that causes you to have your SSI check reduced. Rather, it is your husband's income that causes the check to be reduced once it is added to your household income. Depending on how many people live in the house and how much your husband makes, you may still be eligible for some SSI benefits.