cat is possibly pregnant

i just got a cat from a mutual friend about two weeks ago. she is almost two and not vaccinated or spayed ofc. she is not comfortable with me touching her/getting too close yet. they told me a few weeks ago after i already agreed to take her that she may be pregnant because she felt heavier but that’s about it. they don’t have any idea when there could have been conception. she lived with another male cat who was not neutered. most of the time she is in hiding so its hard to get a good look at her. her belly looks bigger to me and i felt her nipples once when i first got her and they felt firm but i don’t know if that’s normal. i’m pretty sure she is pregnant but not 100%. i cant take her to get an x ray as they keep telling me she must be at least 40 days and i dont have a timeline. she also is not vaccinated so i cannot take her to get an ultrasound. i called multiple vets and they told me pretty much the same thing. i don’t want to waste money and take her for them to check and not be sure. i have no idea what to do in this situation. is it safe for her to get vaccinated while pregnant? i am a first time cat mom so all of this is very new to me and i want to do what’s best for her. do i absolutely have to take her to the vet to be checked out? any advice or input is appreciated.