I feel awful about guest numbers

I feel awful.... After my engagement, some of my coworkers who I have a friendship with asked to be invited to my wedding and I told them that I will try to fit them in. Well I tried but I invited a total of 11 people (including 2 married couples) which is a lot considering I am only having 120 people at my reception. Now some of the single people are asking if they can bring guests. Since I cannot accomodate 18+ people only 11 from my job, I am politely telling them that due to guest # constraints and my big family, I cannot invite them with dates. None of these people are dating someone for more than a year and are good friends to me.
I am beginning to feel that I should not have invited any single people at all since it may cause some ill feelings.

Your thoughts.........:(