I can't believe you did a 42 mile ride after riding only 3 weeks!

I am 53 and I started riding a year ago after not being on a bike at all since I was about 14.
It has taken me a YEAR to go from a 9.5 average speed to a 10.5mpg average. We live in very hilly area. I typically ride about 100 miles per week. My rides vary from 10 miles long to 70 miles.
I go as slow as 2.5mph up steep hills to as fast as 40mph downhill.....but the average comes out to 10.5 overall.

I would say you are doing VERY well so far! It takes MONTHS to build up the muscles in all the places you need them.
Just be proud of yourself and your major accomplishments so far! Your boyfriend should be proud of you too and he should try to enjoy riding with you without watching the computer so much.