Clomid vs metformin

My OBGYN prescribed me clomid after day 3 and day 21 of blood test. 
My primary doctor suggested metformin. 
Now I'm confused, I have not picked up prescription yet. But scared that metformin takes a while. But Clomid seems it is quicker. But my primary doctor scared us when she said multiple pregnancies with clomid....
Any expierence or thoughts about this?