The bike really is to blame though for a part of your issues though. Lugging that extra 6 or 7 pounds of bike up a hill is bad enough. But with gearing that maybe isn't adequate for the speeds you are riding the level parts of your ride and down the other sides of any hill on the route is going to leave you with less energy for that particular climb if keeping up with others in a group is desired. You might need some higher ratio gearing.
For me, just riding that slow up a hill will have me overheat from lack of cooling airflow. Or at least what I'm imagining to be less than 10 mph climbing. If you are faster on the climb then good. It's better than I expected.
The other part is that you still just need to find that pace that allows you to ride all day and at the same time rest between efforts. And by pace I don't really mean cadence or minutes per mile as one might think. It's the muscle you put into pedaling. At any cadence I ride, there is a certain amount of muscle I can use that lets me pedal forever. (yes that's a fisherman's tale or exaggeration) Pedal harder than that and you are now on the timer for how long you can maintain that effort.
And that is where riding more and riding solo will let you find out what that is for you. When riding with others, competition and trying to keep up will only wear you out and make figuring it out harder.
Last edited by Iride01; 06-10-21 at 01:59 PM.