Worry about the reputation of what you do, not of what people think you do.
You can control what you do.
Maras Ayin is only when you are doing something that looks inherently wrong.
Eating pizza isn’t inherently wrong.
I know many people who worry a lot about what people think, and I know many good people.
Rarely are they the same person.
Worrying too much about your reputation can be stressful, destructive, and counter-productive.
The concept is also a little morally backward, because you are worried about social acceptance, as opposed to the real issue.
It occasionally can be a tool for the good, if the correct mentality is used. Rav Miller a”h says that the mishna says to make tocho (the inside) kibaro (like the outside), and not vice versa.
This however, does not mean that one should work on the outside first, rather, if the external motivations are A) already present, and B) cause an action that is objectively good, than one should not stop the “faking,” rather, one should work on the inside to make it real.
Whether or not it is correct for you to go out Motzai Shabbos is a different question, that you need to ask a mentor who knows you. Nothing to do with what others think, more to do with you and how you think.