im going to have a 4th in march 2014 but i do have a friend who has had 5 and it went well . try not to stress . easier said than done but i think it has been long enough for you . it may take longer for them to get threw the tissue but it will be ok :)
I have one friend who never goee into labor, so every baby has been a csection. She had #6 five years ago. After babies 3 and 4 her doc said she would never heal right, shouldn't have any more, etc. After #5, her doc was amazed and said she looked great and gave her the green light for #6. Her uterus had done an excellent job of healing. Its possible her case is rare, but its hard to know since so many people stop having babies after 2 or 3 c sections.