Hello and thank you for using Just Answer. I am sorry to hear about the problems with your boyfriend and his drinking problem. There are two issues that you must consider, If you tell him that you cheated on him, will he leave you? If he then tells you that he cheated on you with someone, will you then leave him? If you both can forgive each other for past wrong doings and want to move forward with the relationship, then that would be wonderful. That does not mean that you have to completely forget about the past. Forgiveness includes letting go of the past and not holding it over someone's head. The person who committed the wrong doing takes responsibility for what they did and then move on. It will take time to rebuild the trust though.
The other issue is the drinking. If he has a drinking problem and it seems to be getting worse, he may need professional assistance. He must come to an awareness that his actions are damaging to the relationship if you are having feelings of mistrust. You will need to sit down and have an open and honest discussion with him regarding his drinking and hanging out with the guys all night. Tell him exactly how you feel. Let him state his opinions. If this is not the type of man that you want in your life and he is not willing to change and he keeps repeating the same behaviors, then you will have to decide to stay, separate for a while, or completely end the relationship.