Fast let down?

So my baby girl was born 3.5 weeks early (she is now 2 weeks old) and exclusively bf. I've noticed over the past few days that when I go to feed her she chokes, like she is getting too much too fast. I always pull her off and pat her back until she stops and sometimes she goes right back to eating (sometimes not). I know she's fine and getting enough food (lots of pees and poops) but it scares me to hear her choke. Is there anything I can do to help her?