Hi I had my 4th CS 9 months ago..my doc recommended that I have no more babies....placenta had attatched itself to the scar tissue and I had a lot of bleeding.
In saying that I am a lot older than you and also I had no problems with number 3 CS. I reckon you would have no problems, you have had good gaps between CS so will have healed well. What about thinking about a VBAC trial, it is lots more common now and you can always go the CS if required.
Goodluck with your decision.