24 yrs old w/1 child. Last 3cycles have been 51, 52, &41 days respectively. Ovulated on cd21 last month. Currently cd13. Around when should I ovulate?

Who knows? There is a predictable 14 days from ovulation to a period. Thus last month you should have had a41-14 or27th day ovulation. I don't know what you are using to judge ovulation timing but i don't think it is correct. I suspect you are not ovulating regularly. Run an ovulation kit. Bbt charts are not very helpful. Inducing regular ovulation is usually easy. Gather information.
2 weeks before. Next period is due. In this situation with the cycles varying from 41-52 days, ovulation could be from day 26 to day 38 of cycle. With periods that far apart and irregular you may not be ovulating every cycle. It is very difficult to predict ovulation when periods are irregular. Reasons for periods to be irregular include thyroid issues, weight gain or loss, too much stress or soy.