I hear ya.
I told myself I would stay on my bike no matter what through winter. Here it is... January is almost over and I have only logged 30 miles on my bike. Not good.
I am scheduled to ride 50 miles today... but sitting here listening to the weather... 32 degrees... with a 15-20 mph wind making the wind chill around 22 degrees. UGH! Just typing that is making me not want to go.
Winter sucks... and yea we do lose some of our fitness over these months. On the upside... others are in the same boat as we are. And when the weather warms up, most of us are all working to get out fitness back.
I know for me... my swimming and running have both improved, just like you. That's good too!
Everything will come back though. No worries. Let your neck rest... and luckily you aren't tempted to ride when the weather is so blah... right?
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"