What to do... it's up to you. If you have hope that your marriage can make it through this and that it won't happen again, then go for resolution between you and your husband.
You can learn to trust again, but it is a huge amount of work and it's a long term endeavor. If you don't think you have the energy, or don't think that your husband has the ability to be faithful, then leave the marriage. Also, If you would like further information and a deeper insight as to what to look for and then what to do go to Eons: Dabeta's Blog and read my story. Wishing you the best!