This is something I struggle with, and as a result so does BS.
1) I lied so much over the last 20+ years that I'm often believing the lies rather than the truth. The simple rule BS has used in the past is that if it does not make sense, then it's a lie. A made up example might be that you felt guilty and wanted to ent the affair when you were with AP. You intended to come home and end the affair and be with your BS. You know this is what you felt. HOWEVER...... You say this felt wrong, you then had sex with your AP, you continued texting and phoning after you returned to BS and even arranged another evening together before d-day actually happened. You cling onto the "I was coming home to you" lie, because you convinced yourself this was true. So much so, that when you're doing your time line you don't even question this....because it's true...Isn't it?!? NO! My point is, write a time line, read it, and then REALLY QUESTION it. ask yourself, what have I minimised, what have I lied about?
2) To your point, not remembering is a BIG point of contention in any attempts at R. You have search history, you have text history, you have credit card history etc etc etc. This gives you and Idea, it gives BS an idea. Maybe, if you TRYELY can't remember (see above) then you might have to adopt a worst case scenario, based on the evidence you have, and then IF something comes to light later down the road, you MAY have the opportunity to lessen the damage caused. I guess it really depends on what you're now confessing. For example, you may be telling BS that you were with AP from 22:00 to 05:00 based on the drinks bill from the bar and a time you remember not being with him. You think you left earlier....but can't remember. In the grand scheme of things, the fact you were with AP is a more important fact than the time you left. Let's say you remember an can prove you got a taxi from the bar at 02:00. This MAY be of some benefit. Of course this does not work if you say you slept with AP once and then a few months later you "remember" it was actually ten times. Also, your past record on lies and TT will impact this.
3) What are you trying to remember? Big or little points? Does BS care about some of the finer points? Spending too much time focused on the wrong thing is detrimental. It goes without saying, it's the BS who gets the say on what is or is not important. Seriously, take a lesson from me, working on what is needed by BS is worth ten time more than working on things you think you need to do.
4) Relax when writing time line (its hard) think clearly and gather your own evidence. Memory is a real shit when it comes to infidelity. You minimise, deny and lie. You don't like looking like the bad person, you hate the feeling that you've utterly destroyed your marriage and your BS. Getting past this and actually remembering and being honest with yourself is painfully difficult.
I'm not saying you're lying or even living with a "tinted" memory. What I am saying is I did! Hey, I'm working through my timeline again to look for minimising and I'm finding shit!! Other WS on here will tell you the same. Things that they KNOW either happened or din not happen, turn out to be untrue. This only becomes obvious once you start to REALLY DEEP DIVE into your memory.
WH (40's) Me. Emotional affair (2017), Physical affair (2003) and online affairs, Two physical affairs (2000). D-Day's 2003, August '17, multiple discoveries through 2018,19 and 20, Jan 21 and 2022