Hi @Highlandttc sorry to hear about your journey. I've also been 3 years TTC, did it the other way round to you with IVF/ ICSI first (using hubby's sperm) and now moved to IUI (donor sperm). Currently hoping for good news for Christmas, but it's a rough ride.
It's great that you got a BFP in August as that shows you can get pregnant.
If you go to IVF, well, it is a bit of a rollercoaster but don't be scared. To be 100% honest I am personally finding IUI much harder. This isn't everyone's experience. But it's the relentlessness of trying month after month with the IUI that gets me - with IVF we had a break of a few months in between rounds so could get a breather.
But I really think if you've done IUI you will be used to the scans and having people poking/ prodding you - that is really the worst bit. The injections for me really weren't so bad once I got used to it, and the egg collection etc is really pretty straightforward.
I would just say be as healthy as you can, do some exercise (but don't overdo it), eat well etc. Don't diet to the extreme but just eat healthy fresh food as much as you can. If you don't have fertility issues yourself then that's all you really need to do, and take folic acid. The other vitamins/ supplements are a bit of a con really if you are generally healthy and have a good diet.
Good luck with it all and fingers crossed for you.