That's a long devastating story dear and I felt every word that has been suffocating you deep inside. It was a relief at least for airing your grievances to your "loving" partner and so untimely to your board exam. Believe me, I can relate to such misery because I've been there, not only once but multiple times that made me a martyr for the sake of our growing kids. To make the story short, it's good that you've uncovered such infidelity at early stage. You still have time to recover and be with your son. Don't cry for people who doesn't deserve your love. Think of your son who needed you the most and try to move on for the better hurting as it may. You don't have to beg for his mercy my dear. Focus on other things to keep yourself busy but don't follow his footsteps because committing another mistake is just like creating another problem. Time heal all wounds but the scar remains so they say so let that scar be a lesson learned to you. Be strong and be firm. Show him that it's his loss not yours. I hope and pray that you will find peace as the days go by. Think of yourself, make a reflection and move forward. God bless.