It can be tough, and general knowledge about gut flora is non-existent, so it’s hard to convince people with the truth. Finding a story that works for you and avoids embarrassment is probably the best idea. Recently diagnosed with allergies, pre-diabetes etc, trying a pro-fertility nutritional plan? I don’t like lying, but it depends on the situation.
As for fertility, if your doctor found nothing that’s surely a good sign, right? Getting yourself healthy first can’t do the cause any harm. Maybe it could even become a source of motivation in these troubling times for you.
I don’t know anything about the topic except bits and pieces that’ve popped up in miscellaneous reading, but I’d look into balancing hormones if you haven’t already. Things like elevated cortisol, unbalanced “sex” hormones, thyroid disturbances etc should raise red lights, and are far from uncommon among people with chronic infections, and can be exasperated (or caused) by stress.