What Is The Cause For Palpitations After I Eat?

I am 30 years old have always been healthy, out of the blue I had a fast pounding heart and nothing else while I was at work. I thought it was something I ate or stress. It worried me and I was reluctant to call the doctor because I didnt have insurance and because I was thinking the worst. After that instance I had a few more episodes of rapid heart and pounding heart, after one episode I did get chills and nausea. Then after about an hour it all went away. I have since went to the cardiologist and he has done lab work and a holter monitor test, echo, and has me scheduled for a stress test. He put me on diltiazem to slow my heart and help lower the BP. I feel as though the blood pressure has dropped but the palpatations or tachycardia still comes generally after I eat. I have never been a big salt person so my diet was minimal salt, and I cut out coffee and soda all together. If I drink anything its water, juice or tea. The palpatations after eating really worry me because it comes almost every time I eat a big meal which is my dinner. My lunch and breakfast are light and healthy. Oh and to my knowledge all tests that have been done have come back ok.