I feel there are very high chances that it is just subconscious double thoughts. However, it can still be a stutter and if it is...you would know yourself in due time because it will aggravate. I am a victim of stammering and you needn't be...so whatever advice I can think of...I immediately feel it can be counter productive incase you do not have a stammer. So, all I can tell you is...if it is a stutter, you would definitely know in time. Do think about what you wanna do about this...whether you want to leave it as it is and just become fluent again or if you want to speak to a speech pathologist.