Why do I say/do weird things?

Like mentioning sex or something gross or revealing too much about myself. I know I'm being weird as it's happening and it's like my insides are screaming don't do____ but I've picked up so much momentum I can't not. I justify saying something in my head before I say it despite subconsciously knowing it's totally strange but then immediately after saying it all those justifications fall away and I'm left feeling really awful wondering why anyone hangs around me and how I'll ever find someone who'll love me. I'm 95% sure I'm not autistic because I'm an empathetic person who tends to be really good at judging social situations, offering advice and support, and making people laugh; like I said it feels like subconsciously I know I'm being/about to be weird but I block out all the warning signs. If I had to describe how I end up looking from the outside when I'm weird it's very David Brent from the British Office.