pregnancy vs ovulation

I have a very irregular cycle. Sometimes I bleed for a three weeks and a week later I will be bleeding again. Sometimes I miss for a month. I am on the oral contraceptive Loestrin-Fe 24 because of this problem. I also am on minocycline. I had sex, during which, we weren't sure when the condom came off. Neither of us finished. I had a period about a week later. Now, (based on a 28 day cycle) I am 5 days late. I took a test it came back negative. I have been stressing a lot lately because of extensive school work. Recently I did some research and I think I am experiencing ovulation due to a think, clear, stretchy, oderless mucus. My question is could I possibly be pregnat even though I had a period right after?