My 6 week old hates his carseat.  He screams from the time he gets in it, the entire ride to store, and riding in the cart.  He's got acid reflux but when being held he enjoys being sat up, pretty much like the position he is in while in his seat.  Any ideas to make venturing out easier, I am starting to feel like a prisoner in my home because it's so difficult to go out with him and my other son (who well behaved dispite being 16 months and having a screaming brother)

Tough one....

Do you have a  base with the car seat?  Maybe try without the base, a different position???  

Timing feedings look at when the acid reflex is at it worse- when his he felling good- I timed trips around nap time.

Can you use a stroller for trips out- maybe do bigger shopping trips when daddy can watch (mom gets a break) then use the stroller and put your stuff in the basket below!  I did this with the double stroller alot!

Sorry not real help 

I FEEL your PAIN!  My son was the same way - screamed the entire time, unless he could feel your touch.  That was fine - a little painful for your arm at time - but when you are the only one in the car, it is not safe and feasible to reach your arm back to comfort him.

There were times that he did not get upset, but those were rare.  The phase ended when he was a little older, I think 9 months if memory serves me correct.

And we were totally done with it when we moved to forward facing.

As for things to do, I had to mix it up with different distractions.  Other then the hand, singing lullabies was the most effective.  And even when it did not work, it helped calm my nerves.

My son was the same way.  Its from the acid reflux.  What are you doing to treat the reflux?  Usually getting the reflux under control helps.  My son never stopped until he was forward facing.  In the infant seat they are laying down to much and makes the reflux worse, sitting up all the way helps keep everything down.  Hope things get better soon.