Jealousy ..

So I have two beautiful kids and we have been debating TTC #3 this summer after a lot of convincing lol. It would be a higher risk pregnancy which with the proper monitoring should be fine. However I’m still nervous about it. I just can’t imagine not having a third. Anyway, two girls I work with are pregnant and I feel so much resentment towards them. Is this normal? I don’t know why I feel this but I feel bad for feeling this way! Ugh.