Looking for the most reliable resources for results of studies on Byetta and Metformin

I'm on the highest (almost - 2500) mgs. of metformin and 10 mcg. Byetta twice a day.  I want to work with my doctor to get the best results but i don't want to gain weight.  I've lost 30 lbs while taking byetta, eating better, and excercising anywhere from 1-3 times a week but now i'm experiencing a flutter in my chest and little pains in the left side of my chest (maybe a stomach nerve?--vagus nerve?).  Didn't have them when i quit taking Byetta for 2 weeks.  Started just 2 days ago and the pains are coming back.  I don't trust just every website for reading but would like to know what is reliable instead of wasting time reading articles that may not be true.  Any advice would be greatly appreciated.