Hang in there, goldfinch, you are doing great. I'm 3 years younger than you, 10 pounds overweight, and have been riding about 6 years. The first ride I went on, DH got me 3 miles from home and I was freaking out because I didn't think I could make it back. We got home and crashed our exhausted bodies on the couch. Three years later, I started running and swimming and did my first triathlon.
I did my first time trial and road races two weeks ago in the Senior Olympics and it was a blast. I got beat in one time trial by a 74 year old! She was very strong, very fast and the same age as my mother (who is sedentary and failing terribly). There were a lot of us over 50's out there who are just getting started so don't let that stop you. It sure beats letting roots grow out your rear because you are sitting around so much!
I would agree that you need a bike fitting and maybe a new saddle. It might be the way the bike is set up and not you or you may even be riding the wrong size bike! Keep plugging along and stay with it.
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"We don't stop playing because we grow old; we grow old because we stop playing." George Bernard Shaw
Luna Eclipse/Selle Italia Lady
Surly Pacer/Terry Butterfly
Quintana Roo Cd01/Koobi Stratus
1981 Schwinn Le Tour Tourist
Jamis Coda Femme