Hello,
That spotting might be premenstrual. Wait until your
pregnancy test. If the result is negative then discontinue taking duphaston. On an average, every female has only 20-25% chances of having a successful conception every month. Since one of your tubes is blocked so pregnancy will occur when the same side of egg ruptures in the unblocked tube.
You can also visit my clinic International Fertility Centre located in Green Park, New Delhi for further evaluation. You can also mail your contact details to reach you.