Women who don't use OPK or BBT

For women who don't use opk or bbt or women who do .. have you actually found it useful to monitor your CM? Like have you found a connection between your CM and possible ovulation dates. I feel like my CM is all over the place from day to day. 27th and 28th was slightly creamy and light, 29th was light and clear now today is creamy and medium. I feel like today is a very good day to BD but I thought I might have possibly already ovulated on the 27th because I had slight pain on my left pelvic side. I'm also already on CD16 would it be normal to ovulate around that time?