I don't mean in bed, I mean on a bike. Does the size of the seat matter? I notice that I can get rather uncomfortable sometimes on my bike seat. It doesn't absorb any shocks and it makes my butt ache. Would you recommend a gel-seat? I'm confused because some people seem to think big seats are better while others seem to think just the opposite. I've heard some people say that a comfy big seat can cause lower back problems and such. What should I do? It's a new bike so maybe my body will get used to it eventually?

Your saddle needs to be wide enough to support your sit bones and firmer tends to be better for anyone who spends time in the saddle as softer saddles tend to put pressure on your softer bits.

In my experience, I've come to realize the difference between a "good" saddle and a "bad" saddle isn't so much the saddle as how you're using it. I always tended to gravitate towards larger, squishier saddles when I first started riding say 20 years ago because when I was sitting on them in a stationary position they felt really comfy and as I learned, that wasn't the case after any length of time in the saddle; my junk was numb, back was sore and all that extra cushioning had turned from ally at the start of the ride to my worst enemy after any length of time. Flash forward to current day and the last thing I want is a soft/squishy saddle...I'd rather have a saddle that my "sit" bones are properly supported on with super thin or even no real padding. I learned to appreciate those saddles that look more like weapons than a seat on a La-Z-Boy once I learned that for any amount of distance (and I don't mean a lot of distance here by any means) it's about learning how to sit so you're sitting on those sit bones and they are properly supported. Once you you learn how to do that, you're money. On a beach cruiser, casual riding or upright bike you're going to ride with your family or around a campground and such, different story...but if you're putting any sort of miles on the bike, learn how to sit on those bones properly and appreciate saddles that look like medieval weaponry

It depends on the type of riding you do. Are you riding a road bike, a mountain bike, a hybrid, etc? Your position determines the stress and pressure on your posterior. Casual short distances on upright bikes lend themselves to wider saddles. Long distances on a road bike are more comfortable (for me at least) on a narrower saddle. Sixty Fiver gave good advice above.

Another question is whether whether or not you're wearing bike shorts. I also find that they make a big difference. Be aware that many cyclist shy away from very thick pads and gel seats or bike shorts because they start to feel like a diaper I've been told.

Last question. Are you new to biking? Almost everyone finds bike seats uncomfortable until your butt becomes used to riding.

^^+1.

The first bike I started on had a miserably uncomfortable saddle. I thought it was because it was small, but later discovered saddles of similar size could be comfortable. The model in question may just be the wrong one for you, or may be a saddle that nobody would ever like. I think on my bike, they did that just so you'd spend an extra $20 on another saddle.

Everybody's different, but not so much that the 100+ saddles can't fit 80% of riders. You just have to find the one that seems to disappear under you. For me, it was the Selle SMP Trk. Tried over a dozen saddles in the last decade, and this one's a keeper.

Don't just sit over the bumps. Use a little pedal pressure to take the weight off your backside, or stand up. Just taking your weight on your feet for a moment can make all the difference.

The style of bike matters. What do you have? If you're on a cruiser that has you sitting bolt upright, then any shock goes right up through your spine. In that case, some sort of sprung saddle might be worth a look.

The shape of the saddle can matter too. For whatever reason, I favor flatter saddles. Ones having a rounded shape from side-to-side cause me pain. Do you have any cycling friends with spare saddles? If you can borrow a few, it pays to experiment.

Posture ... As you are more upright , wider saddles are more common.

crouched down in the aerodynamic racer's position, narrower..

then most of the weight goes onto the pedals, to go faster.

Saddles are completely subjective to each rider.

Time in saddle > less time in saddle
Saddle comfort during exertion > saddle comfort while resting
Firm saddle > squishy saddle
Proper width saddle > too wide or too narrow
Leather > synthetics (generally)
Matched to your application > One size fits all

This after 40 years of riding.