Your lender is required to provide you a loan payment history that documents any payments you have made as well as your principal loan balance over the course of your mortgage. You can compare the loan payment history to your bank statements to confirm that payments you made to the lender are reflected on your mortgage account. If there are differences between your loan payment history and your bank statements you can request that the lender correct any discrepancies. When you make the request, you should provide supporting documents including your bank statements that show that the payments were in fact received.
If the lender refuses to correct your account you should contact a real estate attorney to pursue the matter. If you do not want to pay for a real estate attorney you can contact your state attorney general or the Consumer Finance Protection Bureau (CFPB) to review your situation more closely. It may also be helpful to let your lender know that you are either retaining an attorney or contacting your attorney general or the CFPB. I hope your situation is resolved quickly.