Big sympathy from me. I second whereismycaffeinedrip says and look into the sore tummy or pain possibility.
Some babies are just like this though. Our first son was exactly like you describe. He hated any bouncer chair for more than a minute, sometimes just fastening him into it would make him cry and I'd have to get him straight out again. He cried in his bumbo chair. He couldn't stand the car seat or pushchair.
I carried him in a sling a lot. He wouldn't let me sit down with him either. I spent 9 months pacing around with him because he just didn't want to be still or strapped into anything. Even the high chair caused tantrums and tears.
We looked into everything, we took him to the doctors and health visitors, tried him on reflux medicine incase his tummy was sore, I was so desperate we too him to a cranial osteopath to see if there was something in his body that was causing him discomfort. Nothing changed or made any difference for us but don't rule it out.
For our DS he just didn't like being restricted and made to sit in something. Once he could crawl he was a lot happier to crawl about and play on the floor but still hated the car seat and pushchair really until he could talk and understood that it meant we were going somehwere fun! His talking meant that he understood more and could be distracted if he got bored and chatted to us constantly. Basically he just didn't like being a dependant baby.
It was HARD work. Every time I went to someone's house it would end with him crying and me pacing around trying to distract him. I could literally not sit down with him. It was probably one of the most miserable times of my life 
. His whole babyhood just seems to have been him crying and me standing up holding him and often crying with him!
Good news is it doesn't last forever. They do grow up! DS1 is now 5 and wonderful, I promise he sits down now! He's just always been very independant but is lovely and gentle and just amazing. Do pop to your GP though, often milk intolerances and reflux can cause irritable babies and babies who don't like to sit. Good luck