What to do if I have been complaining about a pain in my lower abs to my doctor for about 5 months and he did nothing but I found out that I had kidney stones?

Anyone who believes they may have a medical malpractice case should contact a medical malpractice lawyer in their area.  These cases are very complicated and depend on the specific circumstances of that case.  You would not want to miss a meritorious case by following the general suggestions of an online lawyer who knows only the few facts you put into your question.

Having said that, I suspect most malpractice lawyers in Michigan will tell you to wait and see what happens after the surgery.  If you recover well, it is good news for you and bad news for a lawsuit.  If you recover well from surgery, the only damages will be the cost of the surgery (which will be paid to your insurance company, not to you), some pain and suffering (which may be quite limited or not allowed at all under Michigan law), and any lost wages you might have (which will be repaid to any disability policy or employer reimbursement you might have).  Out of the small recovery, you would have to pay attorney's fees and the very large costs of hiring experts and prosecuting a malpractice case.

This is why almost every malpractice lawyer in the nation accepts only cases with clear liability and very significant if not catastrophic injuries. 

The complaints of medical lobbies and politicians that people keep getting a windfall from frivolous cases is a flat-out lie.  Don't believe it, and don't believe you can recover a bunch of money just because a medical provider did something wrong.  It does not happen in the real world.  In 30 years of practice in multiple states, I have never seen someone recover anything on a frivolous case.  During this same time period, I have never seen a news story or politician produce accurate facts describing such a recovery.  In addition, every legitimate study of medical malpractice cases, even the studies published in medical journals, show that people recover nothing from frivolous cases and the vast majority of people seriously injured from malpractice never sue or lose their cases. 

You won't get anything from a frivolous case, but you don't want to fall into the large category of people with legitimate malpractice claims who never pursue them either.  The only way to know is to consult with a qualified malpractice lawyer in your area.