I mean... It sounds like an injury.
Regarding fit:
As you've just started out, I think a basic fit is fine. Should cost about 100 bucks without any needed parts and take about an hour ish.
You need to slow down and build up slowly. You shouldn't be ramping up this fast and you shouldn't be doing this much intensity yet. You need to let your body figure things out and adapt before jumping into the intensity or longer rides.
Start with the 20 mile rides, build up to 60 over 5-6 weeks ramping up maybe 10% in length/volume each week. If you end up with another overuse injury like this it's going to take you off the bike for a few weeks again.... Not worth it.