I've been having PVC's for about four months with tachycardia. My...

I've been having PVC's for about four months with tachycardia. My doctor put me on the generic for Toprol -- 50 mg. For two days I was dizzy, faint, weak and nauseated. But no PVC's or tachycardia. Because of side effects my doc decreased the dose to 25mg. five days ago. I felt better. No PVC's or tachycardia, just kind of felt out of it and tired. Yesterday I felt pretty good. My mind was clear and I was less tired, but last night my tachycardia returned with PVC's and I've had them a lot today. Do I need to increase my dose?