New to Forum (again)

Hello again...I posted previously on the "other" forum. This one is probably the better one for this subject. I've kind of run into a wall with my current workout. I've been swimming about 20 laps all freestyle straight through without any rests. That's it. It's getting kind of boring. A little background to my previous swimming...I swam in HS about 30 years ago. Freestyle was the only stroke I swam. I can swim *** stroke and back, but freestyle is the one I use whenever I swim. I have swam off and on since then, but nothing competitive. I enjoy swimming for the physical (and mental) workout, but I definitely feel the need to vary my workout. As it is now, I'm not looking forward to it like I used to. It's become more of a chore which isn't a good way to go about it. My goal is to continue swimming to stay in shape without getting burned out. I'd even consider a Master program if it was in the PM hours versus the AM hours. Work from 7 - 4 so the morning workout is kind of limited. Advice from others that have been though this would be much appreciated. Thanks, Sean