I used cartia. I briefly tried another brand, but I found that it upset my stomach. You can get it from the pharmacy - it's on the shelf, you don't even have to ask for it, generally found with/near the other painkillers.

I'm a slightly different situation - I started it on the day of my embryo transfer, which would equate to a few days after ovulation (can't take it before EPU because of the bleeding risk), but hopefully someone non-IVF will be able to guide you further on what to do with aspirin in relation to more natural conception methods.

BW