Rai, don't take the aspirin unless instructed by your FS. It can be detrimental to some women and cause problems with implantation. It really is an individual thing.
I completely agree with this. There are some people for whom it can be harmful. Best to seek medical advice before starting. Your Dr is likely to support the idea, so I wouldn't worry about being told to not do it. Even the Drs who don't really believe in the immune aspects of IF tend to be comfortable with their patients taking the aspirin.

My current FS has me taking it the entire cycle. My previous FSs only had me take it after O. When I asked my OB about it, he said to just start once I had a BFP. Chat with your Dr about it and see what they recommend. I've never started taking it without first discussing it with a Dr. And that's with knowing it has not caused me any problems in the past...

If you're doing a fresh IVF cycle and are taking it all cycle, you have to stop a few days before EPU. This is where it's particularly important for your Dr to be involved in the decision of whether or not to take it.