Don't apologize. There's no reason for it. Yes you have a Stutter but it doesn't define you. I bet there's more to you then just a speech impediment. Joining social clubs in college is pretty ballsy, imo. Overcoming the fear of meeting new people is 90% of the fight. You should feel great about that. It may be easier to meet with 1 or 2 people so you have more speaking time. Big groups tend to have have a "public speaking" feel to them.