I am approximately 3 months pregnant & currently taking prenatal & folic tablets. Should I take calcium tablets as well?

Not Necessary. As long as your diet has adequate calcium in it and you are taking a good prenatal vitamin, there is no need for additional calcium supplementation. Good Luck with your pregnancy!
You dont have to. Universal recommendation is folic acid, DHA and iron to prevent deformity of brain and spinal cord of the baby and anemia of mom. Calcium is not needed if you eat/drink adequate milk and dairy products. Taking extra calcium 500 mg/day is no harm, but you may be constipated from both iron and Calcium. Take Calcium few hours apart from other meds since calcium can bind with other meds.