It's all that weight you're losing. Your natural cushion is dwindling.

I am tall, 6 foot 2 inches, my desk chair is the most comfortable seat for me in the house. I have it all the way up, it makes it a lot easier for me to get up out of it.

I don`t do couches now, they all seem way too low for me. My next desk chair will probably have an adjustable back on it too if I can find one like that. I need support to sit up straight.

B2You, I went through what you're going through. It went on for years. There was just one chair at home that I could sit in--and it had to be supplied with a special cushion of some kind. I tried air-filled, water-filled, and foam.

When I got my manual wheelchair for distances and bad days, I found that it was really comfortable to sit in because it braced my legs and feet and I could "custom design" the seating. Here again I went through several possibilities but in recent years I've used an inflatable cushion that is indeed costly--but Medicare/Medicaid covers it. It costs about $250.

Comfort doesn't come cheap when you have MS, unfortunately, and I wish this answer didn't involve a wheelchair as I'm sure you don't want to think about that. But it's what worked for me.