Divorce! Each individual is free even if married. Either you trust him, love him, or you outright ask him, or you make sure not to doubt him (you should know how to please him, so that he has no desire to look elsewhere because he is satisfied at home and has no wish to risk that, nor does he feel the need anymore). Otherwise, if you are not capable of that, you know what you have left to do. So make your choice.
Do you love him enough not to think about that, and rather think about living your life, being fulfilled, happy, and shining?
Good luck to you. If you doubt him, you can at most slip a condom into his pocket...
Know that if he wants to, he can hide things from you. So frankly, you need to choose to trust him, accept it, or draw a line under your life together.
