never charted to pinpoint ovulation

had surgery for severe endo 3.5 months ago. tubes were both cleared as both blocked. we've been given the go ahead to TTC and have been charting bbt n cm. this month is my first cycle post medication (lupron) n post op and I have 0 clue how to tell when I ovulate??? my lowest dip was 35.80 then I went up to 36.09c, n up again to 36.28 today (highest its been). I'm day 15 in my cycle. the 35.80 was may 7. it said my best chances to conceive were around that date....so should that mean that's when I ovulated? I would post my chart but have 0 clue how to