Girls are thinking I'm rude

Girls are thinking I'm rude I'm extremely friendly person and i always wanted a friend who is a girl ( you know what I mean) and some girls do come talk to me, but I end up being silent which make them regret there approach I didn't mean to ignore them but my self confidence Hits rock bottom whenever a girl approaches me, I'm fine with boy's I can talk to them for hours (with minimum blocks) but when it's with a girl I'm completely mute. Is this psychological problem or my stuttering stopping me from making connections with girls? The only girl with whom I personally have started a conversation is only with my mom and I'm 20yrs old now. It's a shame that I personally have never started a conversation with girls other than my mom.