Need advice on how to get a married girl?

Ok my bestfriend and me are both married and are wifes are also good friends. In the past we have swapped with oneanother for or plainly swinging. The only problem is my friends wife "sara" and I have very stong feelings for eachother. Now we would never leave our spouses for eachother but there is still strong feelings. The swinging helps greatly to ease the urge for one another but we cant swing everytime we all are together for fear of suspicion. We both want to greatly break the rules and just have without the swinging but she is greatly and me alittle afaid of getting caught. Also without the swinging would be more of an afair. So need advice on what to do?