I don't have advice, but I too have something similar... it's like part of my abdomin is spasming, and I can place my hand on it and feel it. It's weird, and I don't know what causes it. :(
I often feel like my heart is racing, but not in a pounding way... my carotid pulse will feel faint, but fast, and I feel numbness in my body, particularly my hands and feet. If it happens at night as I try to sleep, it feels numb all over, but if I pinch any part I can feel the pain no problem... maybe it's more of a light tingling than numbness. Regardless, it's scared me numerous times at night, and I don't know what on earth causes it.