Lots of good advice here.
You either didn't say, or I missed, how long you have been riding overall. You said since February, but how many years?
I ask because I used to get a lot more of what you're describing when I was in my first year or two of riding. A LOT more. I did a multi-day tour with rides up to 80 miles my first year, so I'm not saying newbies can't go far, etc. But, I do notice that the longer I'm at it, even pushing harder to do more and more, I get what you're describing less and less. I don't know if that has to do with better fueling, more self-knowledge on the bike, or whatever, but there it is.
Also, and this is probably just due to my personality type, I notice that when I ride alone, I feel freer to just really take care of my own needs -- stopping if I need to, eating exactly when I need to, etc. When I ride with others, I tend to put off eating if the pace is high and I feel the need to keep up, or I just don't stop if I feel the need, etc. In the long run, riding with others probably would make me faster by getting me past stopping a lot, etc. But, the added little stress of a group or riding partner can make me a little crankier if it means I'm pushing, pushing, pushing and having to keep someone besides myself in mind.
Just some other stuff to consider...
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury