Let me commend you on your ambition. 6 laps is a lot for the first 2 days. I couldn't even do one lap when I went a few months ago. I haven't gone since. Just walking in the water was hard. I'll go again when school starts and the kids aren't around. But, I was thinking maybe I'll get a massage a few days before I go again. That might help me not to feel like lead. Or not.

As far as your neck hurting, that could be from swimming.

Time between swimming is the best rest you can give your body.