I keep forgetting to take my methotrexate, im starting to get charlie horses. can this be a result from not taking medicine?

Could be: It depends on why you were prescribed methotrexate. If poor adherence to treatment of your autoimmune disorder leads to worsening inflammation or electrolyte abnormalities, that may explain your symptoms.

Hard to say: As it's not clear why you take methotrexate. Remember, as it's very much possible that it is unrelated too. Best to try to make sure you are more consistent about your methotrexate use and if the charlie horses persist or a very debilitating, schedule an appointment with your doctor.