Help ?

My

Im unbelievably confused. If you have missed a period can you still ovulate? I dont have any OPK's as I cant get into town, but i've had tht niggly side which I get each time I ovulate (always on the left). If I missed last period but still testing negative can you still ovulate? Or do you HAVE to have a period to ovulate? Sorry i dont have a clue lol.