Left At The Alter, Should I Stay?

I have been with my boyfriend for 14 years.We recently had two children a two year old and an 8 month old. I found out two days before christmas that he had been sleeping with someone else for two months. Afetr two days of arguing and crying both of us, i agreed to work it out and he promised it would never happen again.He gave me a key to his apartment that night also. In January my little brother was killed and this brought us closer and he asked me to marry him.We set a date to go to city hall and get married on april 21. We were suppose to get married at 3 oclock. At 1:30 he told me he had to go get a haircut. He texted me at 2:14 and said that his barber wasn't there and that we were just leaving at 2:30 to go to city hall. He never showed up.At 2:50 he called and said we werent going to make it to city hall. I have been crying for two days now. He says that he forgot to get the rings and thats the real reason he never came. He says that he still wants us to get married. Our license expires on may 4 and he swears we will get married before it expires. Should i trust him again and give him another chance. I already feel so betrayed, let down, humiliated, and hurt. Do i allow him another chance to hurt me some more, do i just trust in him because I love him or should I just walk away forever.