Right now dd is doing a minimum 3hr15 A time between her naps, most of the time its more, but if she has a really short nap for whatever reason the minimum A time after that would be 3hr15 min. So i bear that in mind, after 3hr15 min i look for little signs. Sometimes she just starts getting whiney, and i know straight away she is ready for nap. She will be more clingy which generally goes hand in hand with the whining (wants me to pick her up) she doesnt really yawn only when i actually put her in the cot. She has a little snuggle blanket and she will grab that and snuggle her face into it & when shes ready for a nap its a bigger face rub/snuggle on the blanket.
Sometimes she can just go forever without showing any tired signs, which is when i have to just put her down for the nap at like a max A time.
I dint think your rubbish at all, some babies are really hard to read, theres nothing you can do about that except guess! So your doing great! And its only because we have been through some of your struggles & got good advice myself that worked that i am able to try & help you.
Really hope you get a good night & WU!