Is it possible to ovulate at the beginning of your fertile window?

My cycles are all over the place. My body is still getting used to not having an antidepressant so my hormones are still crazy.

My cycles are usually 36-38 days long, and I believe I typically ovulate anywhere from CD 18-23.

However, since my period ended, I've mostly had fertile CM except for one day where it was sticky. The rest of the time, it was watery. Yesterday, I had EWCM (CD 13). I believe its the beginning of my fertile window, but I'm just curious if its possible to ovulate at the beginning of your fertile window?

My cervix was also medium-high, soft, and partially open.