Hi katybella.
Not sure how long you have been on the Metformin ?
Some people find it is better to take it half way through a meal rather than before or after. If it is the Met, there are alternatives such as MR/SR versions (slow/modified release). If you have only recently started it it does take a little while to settle down, if it persists see your GP and discuss the alternatives.
Side-effects of Metformin include the following anorexia, nausea, vomiting, diarrhoea (usually transient), abdominal pain, taste disturbance, rarely lactic acidosis (withdraw treatment), decreased vitamin-B12 absorption, erythema, pruritus and urticaria; hepatitis also reported.