Lets be logical

Can somebody give me a logical explanation/reason why my son wants to only be held standing up but when I go to sit down with him he has a absolute meltdown crying and screaming until I get up and start walking with him. I’m telling you that he refuses to let me hold him and sit down with him , he loses his mind . I absolutely can’t wrap my head around why in the world he is like this . I’m quite literally OVER IT. I can’t take much more of the screaming and crying because he’s not being held walked around !!! He screams and cries sitting in his bouncer , activity center , laying on the floor , it does not matter he cries instantly and I literally am about to lose my mind and can’t take much more of it. The ONLY time he doesn’t cry is when we go on walks outside , that’s the ONLY thing he is content with also besides being walked around 24/7. What’s the deal?! I can’t figure it out . He’s been horrible since 6 weeks old and I’m just so sick of it .