Basal Body Temperature readings for avoiding conception

Georgia
I came off hormonal contraceptives recently. Only just learning about FAM, but all this cycle I have been watching my CM, had my most fertile looking stuff around the weekend to Tuesday with weds onwards changing (more like scant stuff now). However only really done my reading and research this week, so I have not been taking Bbt, as I am most likely post ovulation it may be pointless now to chart it. I was so excited last night with thoughts whizzing through my head I really didn't sleep - just rested while thinking. When I took my temp early this morning I felt cold, temp was 35.2. Afterwards I went to toilet then back to bed, a few hours later temp was 36.4*c. I went with first temp because of later movement but is it pointless to record temp now until next cycle? By this weekend I should be safe to not use condoms going just by my CM findings but as its first Month of partial tracking maybe it's better to be extra cautious while getting my pattern. I have read it's basically barren time which is encouraging though.....