Could I be pregnant

I have no idea when I ovulated around the 4th I have spotting and ewcm so I assumed I ovulated that day but now I’m not so sure I took a test on the 13th and it was negative I took another test on the 18 th it was negative to I’m very late on my period and I just wanted to no could I have possibly ovulated later on in my cycle? Could I still be pregnant even tho I got a negative on the 18th ?