Introduction and...where to next?

I am 35 and wife is 32. We have a 3.5 year old son that took 2 or 3 month to concieve. We started trying for #2 18 moths ago and have had no luck.

Intially we knew there was new stress, etc in the home ao we solved that. Wife took a new (less stressful) job, i got adhd meds, etc.

We have had regular sex and are tracking via app, temp, and pee tests. She is pretty regular, but a few that are a week short here and there.

We have gone through testing and both of our hormone levels are normal. Semen had minor irregularity, but nothing that should stop this. She has had every test, except the flushing of her system...whichever one that is. That will be going on this cycle and then ...we have no clue.

We have looked into adoption very minorly so far and my wife feels that she needs the baby phase. With our kid appoaching 4, I want to get this done so they aren't even more spread out.

Is there hope for us? Every doctor has said "nothing looks wrong, but it seems to just not be working"

If we should move on, in the midwest to a middle class family...how long on adoption of an infant that is healthy?