Im struggling.......

We got married in 2011 and she hooked up with someone she worked with in the 1st year. I didn't know what to do, we just got married and bought a house and she swore she only kissed him. Its always been in the back of my mind that wasnt the truth. We adopted 8 kids and she finally admitted to doing more. I've battled with depression and really struggled with everything that happened. What should we do?