Are you on statins for cholesterol ? As you have stated, your liver function tests are abnormal. That is a known side effect of statins. The muscle aches could be due to statin myopathy, another side effect. You should stop taking it till you have consulted a physician regarding your current health.
If your symptoms are explainable as side effects of statin drug therapy, i would not suspect RA as of yet but of course, a proper history, exam and tests are needed for definitive answer. ESR is a non specific finding that is raised whenever the body is in stress or disease state. Getting CPK is warranted as CPK would measure the effects of muscle damage which can be caused by many things including statins.
I would advise to stop taking the statins and get checked.