Lots of people do this. It's almost like a defense mechanism to be self deprecating and put yourself down. I used to do it until a really good friend of mine said "hey, if YOU didn't tell someone that bad thing about yourself, no one would ever guess it or think that". It got me thinking. The world is hard enough without my beating up on myself like that too.
So, a bigger issue though may be to find 'someone' to talk to. Any family? That's a good place to start with a confidant. Like a sibling or cousin? And it sounds like you may be lonely too without any friends or a relationship. Do you desire having those connections in your life? If so, start thinking of ways to branch out. Volunteering is a great one. You have a reason for being somewhere and interact based on the shared volunteer activity . . . but you can build from there. I also have met people doing an exercise class at a gym. You could join a book club. Wine tasting group. take a class at a community college. There are all sorts of options for building your circle around you.
If you feel you MUST talk to coworkers, pick one 'safe' person that you are more friendly with than the others who you think you can trust. talk to just them rather than making derogatory statements about yourself to the group.
And a therapist is a good person to TALK to. That's a psychologist or counselor and you can tell them anything and they share thoughts and ideas. It's not scary to do and doesn't mean there is anything wrong with you if you do this.
Isolation magnifies negative thinking. Now, you might just prefer being alone, lots of people do. But if you don't like being alone, if you have been wanting a romantic relationship, etc., then you have isolated yourself without wanting to. If that's the case, a therapist is a really good idea to find out why you're doing this. Most of us are pretty tribal, humans are a herd animal, so while many do like being alone, it's not our evolutionary nature. Modern society makes it harder because in the modern economic system we're balkanized, not tribal. So people who are alone and don't want to be join something -- sometimes a religious group, sometimes political groups, sometimes a bowling league -- these are essentially substitutes for our tribal nature. Work can be that, too, a lot of people find their adult tribes through work. As far as talking about your "weaknesses," not sure if what you're talking about are really weaknesses or it's just your personality to be self-deprecating. People come in all flavors of personality. It's only a bad thing if it makes you feel bad or it's obsessive. You know which it is, and if it's making you unhappy, it might be insecurity still there from those early experiences of others making you feel unworthy. Therapists are good at working through that kind of thing.