I can totally relate to your pain! I just read this so I may be late to the party! I’m 50 years old and about your size! I ride at least once a week, twice if work and the honey-do-list allows me too! What I have found is riding solo can help you improve in all areas! I ride alone a lot cuz of my work schedule, but this allows me to improve my endurance and work on things at my own pace without chasing the group to keep up! The main thing is don’t give up! As you may have noticed, most guys on the trails are a bit smaller or lighter than we are, I don’t mean to offend anyone at all, but its just fact! However, that doesn’t mean we cant ride too!! I saw someone mentioned a new bike!? Not a bad idea if you can do it! Some of us have a mortgage, car payments, medical bills, insurances, etc.. so we don’t always have extra cash! My advice brother, keep pushing and your skills, wind and your joy for the trails will no doubt improve!!