My Heart Starts To Beat Really Fast After I Eat

my heart starts to beat really fast after I eat and it use to never do this...I exercise frequently during the week 3-5 times a week. I have been also experiencing shortness of breath also after eating and I always crash and go into a food coma. I feel like I have a blood sugar issue because if I don’t eat often I get jittery and shaken and my brain can’t think.