What Causes Rapid Heart Rate And Breathlessness While Taking Gabapentin For Disc Disease?

I have recently been prescribed Gabapentin. I am titrating up to a dose my Orthopedic Dr. wants me to be on. I have a lot of dengenative disc disease and sciatic pain that radiates down my left buttocks and leg. I am also on Warfarin for a past bi-lateral PE. Today I have really felt a shortness of breath and feel like i am actually having fullness feeling in my chest, but more like in my lungs. Am not sick or nor have I been. No chest pain or arm pain. But a very rapid heart beat. I also take Atenolo 25mg QD. Should I make the trip to my Dr. office, which is an hour away, or just wait and see how I feel tomorrow? Just don't feel normal.