Beginner always sliding forward on seat
I'm a similar weight to you and your description is very familiar. I'm almost certain that your saddle is angled down too far. If angling it up enough to stop you slipping causes it to put uncomfortable pressure on your perineum then you probably need a different saddle.

Some people are fine with whatever comes with the bike but I've tried maybe 10 saddles at this point and haven't found one that works well for me. On the bright side, I'm slowly understanding what works and what doesn't.

I'm overweight and it sounds like you are too from your question? I think the extra fat causes issues with the saddle putting pressure on the soft tissues. It also means that gravity is pulling you harder into the saddle.

My poor solution for a long time was to buy a really wide saddle, point it upwards slightly and tilt my pelvis back/arch my back to keep the nose from putting too much pressure on my perineum. This isn't very comfortable though and it seemed to be hard to put out much power. I've recently switched to a bike with a more leant-forward riding position and, while it is great in a number of ways, my old solution absolutely doesn't work.

Here's what I'm looking for in a saddle:


Width - One thing that is immediately obvious to me is that regular width saddles are too narrow. This should be to do with the spacing of the parts of your pelvis that you sit on (and your riding position) rather than having anything to do with weight/fat. I am pretty broadly built so this might not apply to you.
Quantity and softness of padding - Hard, thin padding is better. Lots of soft, squishy padding causes issues with chaffing and when you sink into it, it rises up and puts pressure on your soft bits. I think if you are overweight you need harder padding than normal since you are already more prone to issues with chaffing and because you will sink into it more than a lighter person. Also, I'd rather have bruised bones than a numb penis. Annoyingly, harder saddles are almost always narrower.
Get one with a cutout - Some people like cutouts and some don't but I suspect they are necessary if one is overweight. They can have their own problems though as they can concentrate the pressure along the edges.
Shape - This is really important but it is unfortunately impossible to give recommendations since it is very personal.


Trying out saddles is difficult. Some bike shops have loaner saddles but such places are rare. If you know any cyclists then ask them to led you any spare saddles they have, and ask them to see if their friends have any spare saddles. Even if none of these are comfortable they should give you a better idea of what works and what doesn't.

Extra thoughts:


What kind of seatpost do you have? Some use notches/teeth to hold the saddle angle and in my experience the adjustment on these can be too coarse: one position is too far pointed down but one tooth up is too far pointed up. If you have a seatpost like this that might be the issue as the angle adjustment needed on a saddle is pretty subtle.
"Everyone I talk to gives me the look like they don't have any idea what I'm talking about when I mention it. Could it be that I am just that out of shape?" From bitter experience I know that if your issues are being caused by being overweight then someone who is not overweight probably cannot comprehend it and many will write it off as "not a real problem" even if they are otherwise an expert. I would look for advice from other people in the same boat as you.
From your question I've made the assumption that you are overweight (as opposed to being muscular) but I don't know if this is actually the case. If you are a bodybuilder than some of what I've said holds and some doesn't.