Hello and welcome to EmpowHer,
Typically, Serrapeptase is not a viable treatment for infertility. It is generally used to dissolve the silkworm's cocoon. It can also be taken for inflammation to increase joint health, but more studies that end are non-conclusive. So, I do not recommend taking Serrapeptase for infertility.
Progesterone Cream, on the other hand, can be used for infertility. Its effectiveness will depend on the cause of your infertility.
Below I have pasted a link to an article that lays out the proper steps to using Progesterone Cream.
I hope that helps.