New to Ovulation tests and and I’m very confused!!

So I just got off the pill a month ago, after taking it for 2 months. I’m pretty regular on a 28 day cycle. Af came Oct 1-4 putting my ovulation date around the 15th (so the app says.) We just started trying to conceive last month, yesterday I got some ovulation tests and for fun I took one and the line was dark! So I kinda freaked and took another one at night and same thing a dark line ! So this morning I was still confused so I took another in the morning and again in the evening and the lines were about the same. I’m super confused Af is supposed to come on the 29th is it possible to ovulated just days before your period? Or am I reading these tests wrong and working myself up for nothing? Any advice is greatly appreciated.