My cycles change sometimes too ! Did you take OPKs ? I took them cd 13 which was very faint positive , cd 14 and 15 were negative and then cd 17,18,19,20 were all super strong positives which I thought was strange !
We dtd every day cycle days 9-16 then also cd 17,19, and 21.
Last month I got my period on cycle day 31. We weren't officially trying yet but this month I think we may have put too much pressure on it !