Pregnant rescued feral

[RagingLoons]

We trapped a feral on February 24th. We have been working with her every day and I am able to pet her (sometimes).
I had a gut feeling she was pregnant, so we didn’t spay right away (our other 3 cats are fixed and we weren’t letting her outside obviously).
About 4 days ago I decided she wasn’t pregnant because our male cat was mounting her and she seemed like she was in heat because she was putting her tail up and inviting him on in (he’s a real stud even though he’s fixed).
Then, 3 days ago I noticed her nipples were HUGE. I put my hand on her stomach and felt babies! Pretty aggressive kicking that can be seen from the outside.
She’s been pacing quite a bit, but because she’s feral and new to our family, we really don’t know her normal behavior.
If she had gotten pregnant the day we trapped her, she would be 36 days pregnant, however it could have obviously happened at any point before then. I’ve googled what I can, but I can’t get a definitive answer about how soon before birth you can feel the babies move.
Does anyone have any insight? Insight and advice is greatly appreciated as we’ve never dealt with kittens before (we rescue older cats). And yes, she will be getting spayed as soon as her babies are done nursing!
Thank you in advance!

 

[vince]

About five weeks before birth is where movement can usually be felt and seen. That's only a generalization. It occurs earlier or later with some cats.

Fixed males mounting a female happens. I have one that does occasionally.

 

[Sarthur2]

Don’t let your males mate with her. It’s painful and unnecessary, even though she may invite it. Once you can see and feel kitten movement it’s usually 2-3 weeks until labor and delivery. She’ll need a private place away from your other cats to deliver and nurse her kittens for a few weeks.