Cycle buddy 4/15..confusion

Not really sure how this works. I had a still birth on December 9th at 22 weeks. January 22nd I had a period with bad cramps and heavy flow. The whole month of February there was no period...and 3 negative tests. 42 days later on March 4th I had my period. Which started off really light...which never happens...and I had no cramps...no sore breasts....which has never happened....I've been taking my bbt every days for 2 weeks now and trying to track my CM but its hard to know which app tracks my ovulation the best...I would like someone who is in same boat as me or could shed light