I have a mama rat who dropped 11 3 weeks ago. Since before she dropped she has been in the maternity ward, by herself.

I pulled her out today to weigh the babies, and noticed she looks distinctly pregnant again. She hasn't been with, or anywhere near a male since about a week before she had the 11. Can rats hold over sperm? (I wasnt' thinking so, some fish can, but never heard of mammals that can) If not anybody have any ideas how she could have ended up pregnant or what else could be going on? She's a black berk, so I wouldn't suspect megacolon.

Presuming she actually IS pregnant somehow, should I go ahead and wean her litter? They are eating and drinking good, but still under normal weight that I would wean.