Charting Bbt, On Period?

Ive been charting my bbt and started in the middle of my cycle last month about two weeks after my period. My period was on the 4th of last month and ended on the 8th I started to chart on the 21st, my bbt stayed in between 97.6 and 98.0. Started my period again on the 29th of the same month but the past two days (yesterday(31st) and today(1st)) my bbt has been dropping, yesterday when I checked it was 97.2, today its 96.7.
My question is could my bbt drop while on my period if Im ovulating or does it normally drop when people are on there periods and go back up and drop again when you ovulate? I started my monthly gift on the 29th. Ive started my period twice within the same month its never happened before. Ive also noticed since I had my MC my periods are getting shorter and lighter over time, use to be 5-7days, 2 days out of that being the heaviest now its 3-4 days and like 9-12 hours being the heaviest after the 4th days it just stops all together then the next day or two after I get light spotting here and there.
Been TTC for the past 9 months after my MC(wasn’t planning for the first time to get prego it just happened out of no wheres) but we’ve been having unprotected sex for about 3 years and didn’t think it would happen anytime soon. Now its 5 years since we been together 4 years of unprotected sex and only gotten pregnant once?
Past 9 months my partner and I have been eating healthier, taking vitamins, generally healthy other then the fact we both smoke… (I know smoking doesn’t help TTC been trying to quit) I’m 21 and hes 30.
We don’t “fool around” when I’m on my period I think its kinda gross and messy. Its normally a week we go without sex from the moment I get it to when it stops all together.. Could I have been ovulating on my period? Ive been using a chart online for the last 9 months and having sex on the days its says I should ovulate around but yea nothing..
Any Advice/comments/suggestions would be greatly appreciated,
Thanks!