two wrongs don't make a right

I've been with my boyfriend for three years and we have a two year old son. The first two years where perfect. However, the second year him and a few family members including my dad got into an altercation. It caused a little strain between us but nothing major. Last year around my birthday in March I discovered he had been cheating for months. I called a girl in his phone and she told me they had slept together several times. I was devestated because I had been 100% faithful since the day we got together. I confronted him and he was angry at me for looking in his phone. He later apologized and begged for me to stay. I stayed and never said anything else about it. A month later I went in his phone again and saw that he was still talking to the same girl. He even had text messages from other girls. I couldnt believe it but I stayed because I didnt have the strength to leave. I stopped searching for more lies and eventually started talking to other guys before ending the relationship.

I met one guy in particular and we started hanging out. A fews months passed and we where intimate one night. I stopped seeing him after but continued to talk to him until things fell off. Well to make a long story short my boyfriend found out about everything. Now he is making me feel horrible. I've never believed in cheating and still cant believe Im officially a cheater. It just happened and I feel like I wouldve never done it if he wasnt treating me so bad. My boyfriend used to tell me stuff like "go find another dude if your not happy" when we would argued. I wish I wouldve got out the relationship because he now has reason to find wrong in me. However, unlike him I've admitted I was wrong and learned from this mistake. He never admits that he is wrong. Anyways, I still want to be with him inspite of everything. This man is my first love and I had my first child with him. I feel attached and dont know what to do. We decided to stay together but everyday he is constantly bringing me down about what I did. Why is it so hard to accept and move on? I understand that trust is broken but I've learned the consequence of cheating and never want to be in this situation again. I've given him the password to my voicemail and leave my phone around him all the time. However, it isnt enough for him. I even planned a vacation and made reservations and he says to me today " I think you only want to take a trip because that guy you cheated on me with prob promised you a trip!" Im like are you kidding me. Im beginning to feel hopeless because nothing gets to him. I've actually been thinking about letting it go because he's not mature enough to see that we both lied,betrayed and hurt eachother. I sometimes sit down and think about ending the relationship but its like I cant. He was my first boyfriend, first love and we made a child together. I've never been this attached to a man before. How do you get used to not being around someone you've spent everyday with for three years?