Definitely ask. I'm also dating someone who stutters and my biggest advice is to let him guide you with how you support him. Some days I support my boyfriend by ensuring him that a moment of stuttering was okay or hyping him up for a speaking situation, sometimes I listen to his frustrations or stuttering "wins", sometimes by ordering food through the drive thru because he is having a hard day and doesn't want to. Just be open minded and accepting, which it sounds like you are 😊