How to prepare frozen peas?

Hello!:)

Today I prepared frozen peas by adding them to my pot with pasta in cream sauce and cooking them for 10 minutes over fairly high to medium heat (with the lid on). I stirred them frequently.

Now my question: Was this preparation method okay, or could germs (Listeria) have survived? I'm asking because some of the peas were quite hard inside when I ate them (but the food and the pasta themselves were very hot…)

Which is odd, because I had the peas in the pot for quite a while. Can overcooking peas also cause them to become a bit harder inside? Perhaps the amount of pasta meant that not all of them were covered in the sauce and just needed to cook at the right temperature without too much moisture.

I'm only concerned about the germs because I'm pregnant and don't want to get listeriosis or something similar.

Thank you!:)