Hi, currently I only have one payment method supported in my
Of course, it will hurt your conversion rate.
Yes, you should add more options if you can.
You need both paypal and non-paypal. I've split tested my website and the more payment options you have increases sales no question.
Looking a few years back, it all started with standard credit card purchases, then new methods emerged one by one ... EVERYTIME something new was introduced, vendors reported a raise in sales rates, be it a small or big difference. The effect was different from one country to the next, for example US was always very much CC based, while in EU, it's still not as popular of a payment method... as a result, new payment methods helped more in Europe than in the US. So depends on what GEOs you are targeting too .. if your store is international, you're definitely losing some sales with your current setup.
NOTE: adding a new payment method will help you SOME, but don't expect the sale to double either 