Prayer for my marriage to stay together

My husband and I have been married for 2 years he left me on 5.5.2011 for the third time I have excepted him back each time but right now I feel lonely and like he does not care about my feelings at all after me taking him back I want my marriage to work but how much more can I take we have a 14 year old child involved and I don't want him to think I am a door mat I love him with all my heart but right now I just don't know if I can trust him any longer with my heart.