I know when I'm O'ing because I was very vigilant with my temping plus I used OPKs - now when I think I should be O'ing added with what I know are my signs I take an OPK & it comes up +ve mostly. Saves me using an OPK every day for a week or two. Cheaper!
AFM - after DTD 2 days, 1 day & day of O'ing DH has now COMPLETELY changed his mind & thinks we're not at all in a position to be having a baby hmmm.....hopefully it's too late! He'd be OVER THE MOON if I get a BFP & I know what he's like - he has no CLUE what my cycle is like so will continue to BD when I'm O'ing (not that I'm "tricking" him into anything. He knows we're [were?] trying so not on any BC). He's worse than me with the hot/cold thoughts about this..!