S.M.
Please don't make yourself the bad guy here - counseling is "not enough for you"? You are perfectly justified to be angry and hurt and don't rush yourself to "get over it." He is fantastically lucky to have you because you might the one to save his marriage and family. So take a breath and don't pressure yourself.
Taking action may make you feel better. I would get your ducks in a row in terms of putting aside some money, seeing a lawyer, documenting his behavior. See a doctor and get tested for STDs and make sure yoiu are on birth control. See a therapist independently as well so you can deal with your feelings in a completely open way. You need to protect yourself, because right now, you can't trust him to look out for your best interests or those of your kids. Doing these things, while sad, will make you feel safe. From a position of security, yo will better be able to focus on forgiving him.
I hope that you and your husband can work it out, and deal with any problems in the marriage. But he needs to do ahell of a lot of work on himself and his integrity. He needs to earn back your trust. That won't happen overnight. I know you must jus twant to fix this and forget it because it is less painful. However, if you rush the process, you will always have doubts. Focus on yourself and your kids. Go to counseling, and let him work out his problems. GIve it time - this is a fresh wound. And don't let him rush you. He did this - no matter how bad the marriage, adultery is never a solution. Adultery is a weapon, and how dare he!! Good luck.