First IUI Failed. Hysteroscopy or Receptiva?

Hi Ladies,
I officially got my bloodwork back and its negative for my first IUI which I kind of knew because I tested negative on 13 dpiui. Still waiting for my period though. I can't really decide what to do now?
We have been TTC for 2.5 years now, and I have never seen even a faintest line ever, which means I never conceived.
I have an appointment scheduled with a Napro Doc in Aug and I have a cycle in between. I cant really decide what to do? Should I do another IUI in this cycle with my RE possibly with higher letrozole dose or Ask her to do more testing like hysteroscopy? or endometrial biopsy for endometeritis or endometriosis ? OR
Should I wait to do this testing with my Napro Doc?
IVF is not an option for us.
As for my history:
Super regular cycles (29-31 days), consistent positive OPKs with LP of about 14-15 days.
Partner semen analysis is good (except for lower morphology)
Never spotted in between my cycles.
I do experience twinging/shooting sensation in pelvic area thoughout my cycle, but I am not really sure if its just due to hormones or does it actually mean something.

I would really appreciate any suggestions/thoughts.