We're also debating this question. We're currently in the tww of cycle 5 for baby no.2, and once again pregnancy is not looking likely. This experience is very different from our first time ttc, when I fell pregnant on four out of five cycles (losses before my DD, who's now 17 months). I was 38 at the time, DD born when I was 39. I had to wait a year before trying again due to c-section.
I'm 41 early next year, so quite a bit older than you, OP. I would ideally like to have had a second child before my 43rd birthday, and certainly before my 44th. It's an arbitrary cut off but that's where my mind draws a line. If no pregnancy this month, it's a trip to the GP for us to check for issues, but I'm afraid they won't do much to help given my age and the fact we have one child. We're thinking about going private for fertility tests, and whether we want to travel the IVF route. But we're not rich, and the low success rates for women my age make it especially hard to go for it. I feel very much like we have an extremely tight window for all this to happen. 😞
If I were you I would put age gaps aside for now and, focus on considering the impact ttc might have on your mental health and relationship. Two months is hardly any time at all, and there's no reason you won't conceive spontaneously, but it's no wonder you're anxious based on past experience. If ttc is already stressing you out it's good you're aware of what things might be like for you if it turns into a longer-term endeavour.
Like others have said, a tentative plan to try for 6 months before a trip to the GP is a good idea, and then you can go from there.
If you can't wait though and have the funds, there's nothing stopping you and your DP from having a private fertility MOT. That'll at least give you some information about where you stand, and if necessary, get you on a path to righting anything that could stand in the way of conceiving.
Good luck, OP! I hope next month is your month!