Anyone have any idea what's up?

Hey. So I was supposed to start my period 6 days ago. 4-5 days after ovulation I started to have mild cramps/pains on my left side and I thought MAYBE we finally got lucky this time. Well, I have been testing for the last few days and k keep getting negatives. But since a day or two before my period we about to start I had back pains and cramps. They won't go away and my back pains are pretty severe like they always are the day before AF. I really have no clue why else I would be late other than being pregnant. Should I make an appointment to go see my OBGYN?