I Had My Pacemaker Replaced 3 Days Ago. I Am

I had my pacemaker replaced 3 days ago. I am increasingly short of breath, especially when I lie down. I have an adjustable bed, and sitting up some helps a little. Also, I felt a strong, rapid pulse in my neck on the side of the pacemaker today. Is this normal? I never had any of these issues with the pacemaker I had before, put in in 2007.